Video decoding method and apparatus and video encoding method and apparatus

ABSTRACT

Provided are a video encoding and decoding method and apparatus for obtaining, in a video encoding and decoding process, motion vector resolution information from a bit stream by using a high-level syntax which is a group of information that is applied to a predefined data unit group; determining a motion vector resolution of a current block included in the predefined data unit group based on the motion vector resolution information; determining a prediction motion vector of the current block to be a motion vector of a candidate block from among at least one candidate block, based on the motion vector resolution of the current block; and determining a motion vector of the current block by using the prediction motion vector of the current block.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.16/934,228 filed on Jul. 21, 2020, which is a continuation ofInternational Application No. PCT/KR2019/002377 filed on Feb. 27, 2019,and claims the benefit of U.S. Provisional Application No. 62/636,438,filed on Feb. 28, 2018, in the United States Patent and TrademarkOffice, the disclosures of which are incorporated herein by reference intheir entireties.

TECHNICAL FIELD

The disclosure relates to a video decoding method and apparatus, andmore particularly, to a method and apparatus for encoding an image basedon a motion vector resolution, and a method and apparatus for decodingan image.

BACKGROUND ART

In a video encoding and decoding method, a picture is split into macroblocks, and each macro block is prediction-encoded through interprediction or intra prediction, in order to encode an image.

The inter prediction is a method of removing temporal redundancy betweenpictures to compress an image. A representative example of the interprediction is motion estimation coding. The motion estimation codingpredicts blocks of a current picture using a reference picture. Areference block that is most similar to a current block is searchedwithin a predefined search range by using a predefined evaluationfunction.

The current block is predicted based on the reference block, and aprediction block generated as the result of the prediction is subtractedfrom the current block to generate a residual block. The residual blockis then encoded. To more accurately perform the prediction,interpolation is performed on the search range of the reference pictureto generate pixels in a sub pel unit that is smaller than an integer pelunit, and inter prediction is performed based on the pixels in the subpel unit.

In a codec, such as H.264 Advanced Video Coding (AVC) and HighEfficiency Video Coding (HEVC), motion vectors of previously encodedblocks being adjacent to a current block or blocks included in apreviously encoded picture are used as prediction motion vectors of thecurrent block in order to predict a motion vector of the current block(Motion Vector Prediction).

DESCRIPTION OF EMBODIMENTS Technical Problem

To apply Adaptive Motion Vector Resolution (AMVR) in a process for videoencoding and decoding, a method and apparatus for using motion vectorresolution information of a high-level syntax which is a group ofinformation applied to a predefined data unit group are proposed. Morespecifically, a method and apparatus for applying AMVR to a currentblock included in a high-level unit (a unit of a sequence, a picture, aslice, or a tile) using motion vector resolution information signaled toa high-level syntax are proposed.

Solution to Problem

To overcome the above-described technical problem, a video decodingmethod proposed in the disclosure includes: obtaining motion vectorresolution information from a bit stream by using a high-level syntaxincluding a group of information applied to a predefined data unitgroup; determining a motion vector resolution of a current blockincluded in the predefined data unit group based on the motion vectorresolution information; determining a prediction motion vector of thecurrent block to be a motion vector of a candidate block from among atleast one candidate block, based on the motion vector resolution of thecurrent block; and determining a motion vector of the current block byusing the prediction motion vector of the current block.

To overcome the above-described technical problem, a video decodingapparatus proposed in the disclosure includes: a memory; and at leastone processor connected to the memory, wherein the at least oneprocessor is configured to obtain motion vector resolution informationfrom a bit stream by using a high-level syntax including a group ofinformation applied to a predefined data unit group, determine a motionvector resolution of a current block included in the predefined dataunit group based on the motion vector resolution information, determinea prediction motion vector of the current block to be a motion vector ofa candidate block from among at least one candidate block, based on themotion vector resolution of the current block, and determine a motionvector of the current block by using the prediction motion vector of thecurrent block.

To overcome the above-described technical problem, a video encodingmethod proposed in the disclosure includes: performing motion predictionon a current block to determine a motion vector and a motion vectorresolution of the current block; determining a prediction motion vectorof the current block to be a motion vector from among at least onecandidate block, based on the motion vector resolution; determining aresidual motion vector of the current block by using the predictionmotion vector of the current block; and encoding the motion vectorresolution information representing the motion vector resolution with ahigh-level syntax which is a group of information that is applied to apredefined data unit group, and encoding the residual motion vector ofthe current block.

To overcome the above-described technical problem, a video encodingapparatus proposed in the disclosure includes: a memory; and at leastone processor connected to the memory, wherein the at least oneprocessor is configured to: perform motion prediction on a current blockto determine a motion vector and a motion vector resolution of thecurrent block; determine a prediction motion vector of the current blockto be a motion vector from among at least one candidate block, based onthe motion vector resolution; determine a residual motion vector of thecurrent block by using the prediction motion vector of the currentblock; and encode the motion vector resolution information representingthe motion vector resolution with a high-level syntax which is a groupof information that is applied to a predefined data unit group, andencode the residual motion vector of the current block.

Advantageous Effects of Disclosure

By using information of a high-level syntax, such as a sequence level, apicture level, a slice level, or a tile level, etc., to apply AdaptiveMotion Vector Resolution (AMVR) in a process for video encoding anddecoding, a bit rate may be saved and encoding efficiency andperformance may be improved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic block diagram of an image decoding apparatusaccording to an embodiment.

FIG. 2 is a flowchart of an image decoding method according to anembodiment.

FIG. 3 illustrates a process, performed by an image decoding apparatus,of determining at least one coding unit by splitting a current codingunit, according to an embodiment.

FIG. 4 illustrates a process, performed by an image decoding apparatus,of determining at least one coding unit by splitting a non-square codingunit, according to an embodiment.

FIG. 5 illustrates a process, performed by an image decoding apparatus,of splitting a coding unit based on at least one of block shapeinformation and split shape mode information, according to anembodiment.

FIG. 6 illustrates a method, performed by an image decoding apparatus,of determining a predefined coding unit from among an odd number ofcoding units, according to an embodiment.

FIG. 7 illustrates an order of processing a plurality of coding unitswhen an image decoding apparatus determines the plurality of codingunits by splitting a current coding unit, according to an embodiment.

FIG. 8 illustrates a process, performed by an image decoding apparatus,of determining that a current coding unit is to be split into an oddnumber of coding units, when the coding units are not processable in apredefined order, according to an embodiment.

FIG. 9 illustrates a process, performed by an image decoding apparatus,of determining at least one coding unit by splitting a first codingunit, according to an embodiment.

FIG. 10 illustrates that a shape into which a second coding unit issplittable is restricted when the second coding unit having a non-squareshape, which is determined when an image decoding apparatus splits afirst coding unit, satisfies a predefined condition, according to anembodiment.

FIG. 11 illustrates a process, performed by an image decoding apparatus,of splitting a square coding unit when split shape mode information isunable to indicate that the square coding unit is split into four squarecoding units, according to an embodiment.

FIG. 12 illustrates that a processing order between a plurality ofcoding units may be changed depending on a process of splitting a codingunit, according to an embodiment.

FIG. 13 illustrates a process of determining a depth of a coding unitwhen a shape and size of the coding unit change, when the coding unit isrecursively split such that a plurality of coding units are determined,according to an embodiment.

FIG. 14 illustrates depths that are determinable based on shapes andsizes of coding units, and part indexes (PIDs) that are fordistinguishing the coding units, according to an embodiment.

FIG. 15 illustrates that a plurality of coding units are determinedbased on a plurality of predefined data units included in a picture,according to an embodiment.

FIG. 16 illustrates a processing block serving as a criterion fordetermining a determination order of reference coding units included ina picture, according to an embodiment.

FIG. 17 is a block diagram of a video encoding apparatus according to anembodiment.

FIG. 18 is a flowchart of a video encoding method according to anembodiment.

FIG. 19 is a block diagram of a video decoding apparatus according to anembodiment.

FIG. 20 is a flowchart of a video decoding method according to anembodiment.

FIG. 21 illustrates an interpolation method for determining motionvectors according to various motion vector resolutions.

FIG. 22A, FIG. 22B, FIG. 22C, and FIG. 22D illustrate locations ofpixels that may be indicated by motion vectors in correspondence to a ¼pel unit Motion Vector Resolution (MVR), a ½ pel unit MVR, a 1 pel unitMVR, and a 2 pel unit MVR, when a supportable minimum MVR is a ¼ pelunit MVR.

FIG. 23 illustrates an example of determining a motion vector resolutionindex using a high-level syntax.

FIG. 24 illustrates another example of determining a motion vectorresolution index in a high-level syntax.

FIG. 25 illustrates a structure of temporal layers for a Group ofPictures (GOP).

FIGS. 26A and 26B illustrate a method for adjusting a prediction motionvector.

FIG. 27 illustrates at least one candidate block 1:1 mapped to at leastone candidate MVR.

FIG. 28 illustrates an example of a mapping relationship between atleast one candidate motion vector resolution and at least one candidateblock.

FIG. 29 illustrates processing modes respectively included in predictionprocessing, transform processing, and filtering processing.

FIG. 30 illustrates an example of applicable processing modes ornon-applicable processing modes predefined for MVRs.

FIG. 31 illustrates an example of applicable processing modes ornon-applicable processing modes predefined for MVRs.

FIG. 32 illustrates an example of applicable processing modes ornon-applicable processing modes predefined for MVRs.

BEST MODE

A video decoding method according to an embodiment proposed in thedisclosure includes: obtaining motion vector resolution information froma bit stream by using a high-level syntax which is a group ofinformation that is applied to a predefined data unit group; determininga motion vector resolution of a current block included in the predefineddata unit group based on the motion vector resolution information;determining a prediction motion vector of the current block to be amotion vector from among a candidate block of at least one candidateblock, based on the motion vector resolution of the current block; anddetermining a motion vector of the current block by using the predictionmotion vector of the current block.

According to an embodiment, when a candidate motion vector resolution ofthe candidate block is different from the motion vector resolution ofthe current block, the video decoding method may further includedetermining the prediction motion vector of the current block byadjusting the motion vector of the candidate block.

According to an embodiment, the motion vector resolution informationincludes start resolution location information, and the video decodingmethod may further include: determining at least one motion vectorresolution index from a predefined motion vector set including aplurality of resolutions sequentially arranged, based on the startresolution location information; and determining the motion vectorresolution of the current block, based on the at least one motion vectorresolution index.

According to an embodiment, the motion vector resolution information mayinclude motion vector resolution set information, and the video decodingmethod may further include: determining a motion vector resolution setof a plurality of motion vector resolution sets, based on the motionvector resolution set information; and determining the motion vectorresolution of the current block, based on at least one motion vectorresolution index determined based on the motion vector resolution set.

According to an embodiment, the motion vector resolution information mayinclude at least one motion vector resolution index respectivelycorresponding to at least one motion vector resolution, and the videodecoding method may further include determining the motion vectorresolution of the current block, based on the at least one motion vectorresolution index.

According to an embodiment, the video decoding method may furtherinclude: obtaining information about whether or not to use an absolutevalue of a difference between a reference frame Picture Order Count(POC) and a current frame POC from the bit stream by using thehigh-level syntax; and determining the motion vector resolution of thecurrent block, based on the absolute value of the difference between thereference frame POC and the current frame POC and a predefined thresholdvalue.

According to an embodiment, the motion vector resolution information mayinclude information about a maximum number of motion vector resolutionindices.

According to an embodiment, the motion vector resolution information mayinclude information about a difference between the number of motionvector resolution indices and a predefined minimum number of motionvector resolution indices.

According to an embodiment, the predefined minimum number of the motionvector resolution indices may be classified according to temporallayers.

According to an embodiment, the video decoding method may furtherinclude: obtaining configuration information for a motion vectorcandidate list from the bit stream by using the high-level syntax,wherein the configuration information for the motion vector candidatelist represents whether or not to use at least one of a candidate motionvector list for at least one candidate block of the current block and amotion vector list of predefined blocks respectively corresponding tocandidate motion vector resolutions of the current block; anddetermining the motion vector of the current block, based on theconfiguration information for the motion vector candidate list.

According to an embodiment, the video decoding method may furtherinclude: obtaining information about whether or not to execute at leastone processing mode according to the motion vector resolution of thecurrent block from a plurality of processing modes included in at leastone processing among prediction processing, transform processing, andfiltering processing for decoding the current block, from the bitstream, by using the high-level syntax; and decoding the current blockbased on the information about whether or not to execute the at leastone processing mode.

According to an embodiment, the information about whether or not toexecute the at least one processing mode may include default settingchanging information, and the video decoding method may further includeupdating the information about whether or not to execute the at leastone processing mode when the default setting changing informationrepresents that whether or not to execute the at least one processingmode changes.

According to an embodiment, the high-level syntax may be one of asequence level syntax, a picture level syntax, a slice level syntax, anda tile level syntax.

A video encoding method according to an embodiment proposed in thedisclosure includes: performing motion prediction on a current block todetermine a motion vector and a motion vector resolution of the currentblock; determining a motion vector of at least one candidate block as aprediction motion vector of the current block, based on the motionvector resolution; determining a residual motion vector of the currentblock by using the prediction motion vector of the current block; andencoding the motion vector resolution information representing themotion vector resolution with a high-level syntax which is a group ofinformation that is applied to a predefined data unit group, andencoding the residual motion vector of the current block.

A video decoding apparatus according to an embodiment proposed in thedisclosure includes: a memory; and at least one processor connected tothe memory, wherein the at least one processor is configured to obtainmotion vector resolution information from a bit stream by using ahigh-level syntax which is a group of information that is applied to apredefined data unit group, determine a motion vector resolution of acurrent block included in the predefined data unit group based on themotion vector resolution information, determine a prediction motionvector of the current block to be a motion vector from among a candidateblock of at least one candidate block, based on the motion vectorresolution of the current block, and determine a motion vector of thecurrent block by using the prediction motion vector of the currentblock.

Mode of Disclosure

Advantages and features of one or more embodiments and methods ofaccomplishing the same may be understood more readily by reference tothe embodiments and the accompanying drawings. In this regard, theembodiments of the disclosure may have different forms and should not beconstrued as being limited to the descriptions set forth herein. Rather,these embodiments are provided so that this disclosure will be thoroughand complete and will fully convey the concept of the presentembodiments of the disclosure to one of ordinary skill in the art.

The terms used in the specification will be briefly defined, and theembodiments will be described in detail.

All terms including descriptive or technical terms which are used hereinshould be construed as having meanings that are obvious to one ofordinary skill in the art. However, the terms may have differentmeanings according to the intention of one of ordinary skill in the art,precedent cases, or the appearance of new technologies. Also, some termsmay be arbitrarily selected by the applicant, and in this case, themeaning of the selected terms will be described in detail in thedetailed description of the disclosure. Thus, the terms used herein haveto be defined based on the meaning of the terms together with thedescription throughout the specification.

In the following specification, the singular forms include plural formsunless the context clearly indicates otherwise.

When a part “includes” or “comprises” an element, unless there is aparticular description contrary thereto, the part may further includeother elements, not excluding the other elements.

In the following description, terms such as “unit” indicate a softwareor hardware component and the “unit” performs certain functions.However, the “unit” is not limited to software or hardware. The “unit”may be formed so as to be in an addressable storage medium, or may beformed so as to operate one or more processors. Thus, for example, theterm “unit” may refer to components such as software components,object-oriented software components, class components, and taskcomponents, and may include processes, functions, attributes,procedures, subroutines, segments of program code, drivers, firmware,micro codes, circuits, data, a database, data structures, tables,arrays, or variables. A function provided by the components and “units”may be associated with the smaller number of components and “units”, ormay be divided into additional components and “units”.

According to an embodiment of the disclosure, the “unit” may include aprocessor and a memory. The term “processor” should be interpretedbroadly to include a general purpose processor, a central processingunit (CPU), a microprocessor, a digital signal processor (DSP), acontroller, a microcontroller, a state machine, and the like. In somecircumstances, the “processor” may refer to an application specificsemiconductor (ASIC), a programmable logic device (PLD), a fieldprogrammable gate array (FPGA), or the like. The term “processor” mayrefer to a combination of processing devices such as, for example, acombination of a DSP and a microprocessor, a combination of a pluralityof microprocessors, a combination of one or more microprocessors inconjunction with a DSP core, or a combination of any other suchconfiguration.

The term “memory” should be interpreted broadly to include anyelectronic component capable of storing electronic information. The term“memory” may refer to various types of processor-readable media, such asa random access memory (RAM), a read-only memory (ROM), a non-volatilerandom access memory (NVRAM), a programmable read-only memory (PROM), anerase-programmable read-only memory (EPROM), an electrically erasablePROM (EEPROM), a flash memory, a magnetic or optical data storagedevice, a register, and the like. When the processor can readinformation from a memory and/or write information to the memory, thememory is said to be in an electronic communication state with theprocessor. The memory integrated in the processor is in an electroniccommunication state with the processor.

Hereinafter, an “image” may be a static image such as a still image of avideo or may be a dynamic image such as a moving image, that is, thevideo itself.

Hereinafter, a “sample” denotes data assigned to a sampling position ofan image, i.e., data to be processed. For example, pixel values of animage in a spatial domain and transform coefficients on a transformregion may be samples. A unit including at least one such sample may bedefined as a block.

Also, in the present specification, a ‘current block’ may mean a blockof a maximum encoding unit, an encoding unit, a prediction unit, or atransform unit of a current image that is to be encoded or decoded.

Also, in the present specification, a ‘motion vector resolution’ maymean precision of a location of a pixel which may be indicated by amotion vector determined through inter prediction, among pixels includedin a reference image (or an interpolated reference image). That a motionvector resolution has a N pel unit (N is a rational number) means thatthe motion vector may have precision of a N pel unit. For example, amotion vector resolution of a ¼ pel unit may mean that the motion vectormay indicate a pixel location of the ¼ pel unit (that is, a sub pelunit) in an interpolated reference image, and a motion vector resolutionof a 1 pel unit may mean that the motion vector may indicate a pixellocation corresponding to the 1 pel unit (that is, an integer pel unit)in an interpolated reference image.

Also, in the present specification, a ‘candidate motion vectorresolution’ means at least one motion vector resolution that may beselected as a motion vector resolution of a block, and a ‘candidateblock’ means at least one block that may be used as a block for aprediction motion vector of a block mapped to a candidate motion vectorresolution and inter-predicted.

Also, in the present specification, a ‘pel unit’ may be referred to aspixel precision, pixel accuracy, or the like.

Hereinafter, embodiments will be described in detail with reference tothe accompanying drawings such that one of ordinary skill in the art mayeasily implement the embodiments. In the drawings, parts irrelevant tothe description are omitted to clearly describe the present disclosure.

Hereinafter, an image encoding apparatus and an image decodingapparatus, and an image encoding method and an image decoding methodaccording to embodiments will be described with reference to FIGS. 1 to16. A method of determining a data unit of an image, according to anembodiment, will be described with reference to FIGS. 3 to 16, and avideo decoding method of obtaining motion vector resolution informationusing a high-level syntax which is a group of information that isapplied to a predefined data unit group, determining a motion vectorresolution of a current block included in the predefined data unit groupbased on the motion vector resolution information, determining a motionvector of a candidate block of at least one candidate block as aprediction motion vector of the current block based on the motion vectorresolution of the current block, and determining a motion vector of thecurrent block by using the prediction motion vector of the currentblock, according to an embodiment, will be described with reference toFIGS. 17 to 32.

Hereinafter, a method and apparatus for adaptively selecting a contextmodel, based on various shapes of coding units, according to anembodiment of the disclosure, will be described with reference to FIGS.1 and 2.

FIG. 1 is a schematic block diagram of an image decoding apparatusaccording to an embodiment.

An image decoding apparatus 100 may include a receiver 110 and a decoder120. The receiver 110 and the decoder 120 may include at least oneprocessor. Also, the receiver 110 and the decoder 120 may include amemory storing instructions to be performed by the at least oneprocessor.

The receiver 110 may receive a bitstream. The bitstream includesinformation of an image encoded by an image encoding apparatus 2200described later. Also, the bitstream may be transmitted from the imageencoding apparatus 2200. The image encoding apparatus 2200 and the imagedecoding apparatus 100 may be connected via wires or wirelessly, and thereceiver 110 may receive the bitstream via wires or wirelessly. Thereceiver 110 may receive the bitstream from a storage medium, such as anoptical medium or a hard disk. The decoder 120 may reconstruct an imagebased on information obtained from the received bitstream. The decoder120 may obtain, from the bitstream, a syntax element for reconstructingthe image. The decoder 120 may reconstruct the image based on the syntaxelement.

Operations of the image decoding apparatus 100 will be described indetail with reference to FIG. 2.

FIG. 2 is a flowchart of an image decoding method according to anembodiment.

According to an embodiment of the disclosure, the receiver 110 receivesa bitstream.

The image decoding apparatus 100 obtains, from a bitstream, a bin stringcorresponding to a split shape mode of a coding unit (operation 210).The image decoding apparatus 100 determines a split rule of the codingunit (operation 220). Also, the image decoding apparatus 100 splits thecoding unit into a plurality of coding units, based on at least one ofthe bin string corresponding to the split shape mode and the split rule(operation 230). The image decoding apparatus 100 may determine anallowable first range of a size of the coding unit, according to a ratioof the width and the height of the coding unit, so as to determine thesplit rule. The image decoding apparatus 100 may determine an allowablesecond range of the size of the coding unit, according to the splitshape mode of the coding unit, so as to determine the split rule.

Hereinafter, splitting of a coding unit will be described in detailaccording to an embodiment of the disclosure.

First, a picture may be split into at least one slice or at least onetile. A slice or tile may be a sequence of at least one Coding Tree Unit(CTU). As a concept contrasted with the CTU, there is a Coding TreeBlock (CTB).

The largest coding unit (CTB) denotes an N×N block including N×N samples(N is an integer). Each color component may be split into one or morelargest coding blocks.

When a picture has three sample arrays (sample arrays for Y, Cr, and Cbcomponents), a largest coding unit (CTU) includes a largest coding blockof a luma sample, two corresponding largest coding blocks of chromasamples, and syntax structures used to encode the luma sample and thechroma samples. When a picture is a monochrome picture, a largest codingunit includes a largest coding block of a monochrome sample and syntaxstructures used to encode the monochrome samples. When a picture is apicture encoded in color planes separated according to color components,a largest coding unit includes syntax structures used to encode thepicture and samples of the picture.

One largest coding block (CTB) may be split into M×N coding blocksincluding M×N samples (M and N are integers).

When a picture has sample arrays for Y, Cr, and Cb components, a codingunit (CU) includes a coding block of a luma sample, two correspondingcoding blocks of chroma samples, and syntax structures used to encodethe luma sample and the chroma samples. When a picture is a monochromepicture, a coding unit includes a coding block of a monochrome sampleand syntax structures used to encode the monochrome samples. When apicture is a picture encoded in color planes separated according tocolor components, a coding unit includes syntax structures used toencode the picture and samples of the picture.

As described above, a largest coding block and a largest coding unit areconceptually distinguished from each other, and a coding block and acoding unit are conceptually distinguished from each other. That is, a(largest) coding unit refers to a data structure including a (largest)coding block including a corresponding sample and a syntax structurecorresponding to the (largest) coding block. However, because it isunderstood by one of ordinary skill in the art that a (largest) codingunit or a (largest) coding block refers to a block of a predefined sizeincluding a predefined number of samples, a largest coding block and alargest coding unit, or a coding block and a coding unit are mentionedin the following specification without being distinguished unlessotherwise described.

An image may be split into largest coding units (CTUs). A size of eachlargest coding unit may be determined based on information obtained froma bitstream. A shape of each largest coding unit may be a square shapeof the same size. However, an embodiment is not limited thereto.

For example, information about a maximum size of a luma coding block maybe obtained from a bitstream. For example, the maximum size of the lumacoding block indicated by the information about the maximum size of theluma coding block may be one of 4×4, 8×8, 16×16, 32×32, 64×64, 128×128,and 256×256.

For example, information about a luma block size difference and amaximum size of a luma coding block that may be split in 2 may beobtained from a bitstream. The information about the luma block sizedifference may refer to a size difference between a luma largest codingunit and a largest luma coding block that may be split in 2.Accordingly, when the information about the maximum size of the lumacoding block that may be split in 2 and the information about the lumablock size difference obtained from the bitstream are combined with eachother, a size of the luma largest coding unit may be determined. A sizeof a chroma largest coding unit may be determined by using the size ofthe luma largest coding unit. For example, when a Y:Cb:Cr ratio is 4:2:0according to a color format, a size of a chroma block may be half a sizeof a luma block, and a size of a chroma largest coding unit may be halfa size of a luma largest coding unit.

According to an embodiment, because information about a maximum size ofa luma coding block that is binary splittable is obtained from abitstream, the maximum size of the luma coding block that is binarysplittable may be variably determined. In contrast, a maximum size of aluma coding block that is ternary splittable may be fixed. For example,a maximum size of a luma coding block that may be ternary split in an Ipicture may be 32×32, and a maximum size of a luma block that may beternary split in a P picture or a B picture may be 64×64.

Also, a largest coding unit may be hierarchically split into codingunits based on split shape mode information obtained from a bitstream.At least one of information indicating whether quad splitting isperformed, information indicating whether multi-splitting is performed,split direction information, and split type information may be obtainedas the split shape mode information from the bitstream.

For example, the information indicating whether quad splitting isperformed may indicate whether a current coding unit is quad split(QUAD_SPLIT) or not.

When the current coding unit is not quad split, the informationindicating whether multi-splitting is performed may indicate whether thecurrent coding unit is no longer split (NO_SPLIT) or binary/ternarysplit.

When the current coding unit is binary split or ternary split, the splitdirection information indicates that the current coding unit is split inone of a horizontal direction and a vertical direction.

When the current coding unit is split in the horizontal direction or thevertical direction, the split type information indicates that thecurrent coding unit is binary split or ternary split.

A split mode of the current coding unit may be determined according tothe split direction information and the split type information. A splitmode when the current coding unit is binary split in the horizontaldirection may be determined to be a binary horizontal split mode(SPLIT_BT_HOR), a split mode when the current coding unit is ternarysplit in the horizontal direction may be determined to be a ternaryhorizontal split mode (SPLIT_TT_HOR), a split mode when the currentcoding unit is binary split in the vertical direction may be determinedto be a binary vertical split mode (SPLIT_BT_VER), and a split mode whenthe current coding unit is ternary split in the vertical direction maybe determined to be a ternary vertical split mode (SPLIT_TT_VER.

The image decoding apparatus 100 may obtain, from the bitstream, thesplit shape mode information from one bin string. A form of thebitstream received by the image decoding apparatus 100 may include fixedlength binary code, unary code, truncated unary code, pre-determinedbinary code, or the like. The bin string is information in a binarynumber. The bin string may include at least one bit. The image decodingapparatus 100 may obtain the split shape mode information correspondingto the bin string, based on the split rule. The image decoding apparatus100 may determine whether to quad-split a coding unit, whether not tosplit a coding unit, a split direction, and a split type, based on onebin string.

The coding unit may be smaller than or same as the largest coding unit.For example, because a largest coding unit is a coding unit having amaximum size, the largest coding unit is one of coding units. When splitshape mode information about a largest coding unit indicates thatsplitting is not performed, a coding unit determined in the largestcoding unit has the same size as that of the largest coding unit. Whensplit shape code information about a largest coding unit indicates thatsplitting is performed, the largest coding unit may be split into codingunits. Also, when split shape mode information about a coding unitindicates that splitting is performed, the coding unit may be split intosmaller coding units. However, the splitting of the image is not limitedthereto, and the largest coding unit and the coding unit may not bedistinguished. The splitting of the coding unit will be described indetail with reference to FIGS. 3 through 16.

Also, one or more prediction blocks for prediction may be determinedfrom a coding unit. The prediction block may be the same as or smallerthan the coding unit. Also, one or more transform blocks for transformmay be determined from a coding unit. The transform block may be thesame as or smaller than the coding unit.

The shapes and sizes of the transform block and prediction block may notbe related to each other.

In another embodiment, prediction may be performed by using a codingunit as a prediction unit. Also, transformation may be performed byusing a coding unit as a transform block.

The splitting of the coding unit will be described in detail withreference to FIGS. 3 to 16. A current block and an adjacent block of thedisclosure may indicate one of the largest coding unit, the coding unit,the prediction block, and the transform block. Also, the current blockof the current coding unit is a block that is currently being decoded orencoded or a block that is currently being split. The adjacent block maybe a block reconstructed before the current block. The adjacent blockmay be adjacent to the current block spatially or temporally. Theadjacent block may be located at one of the lower left, left, upperleft, top, upper right, right, lower right of the current block.

FIG. 3 illustrates a process, performed by the image decoding apparatus,of determining at least one coding unit by splitting a current codingunit, according to an embodiment.

A block shape may include 4N×4N, 4N×2N, 2N×4N, 4N×N, N×4N, 32N×N, N×32N,16N×N, N×16N, 8N×N, or N×8N. Here, N may be a positive integer. Blockshape information is information indicating at least one of a shape,direction, a ratio of width and height, or size of a coding unit.

The shape of the coding unit may include a square and a non-square. Whenthe lengths of the width and height of the coding unit are the same(i.e., when the block shape of the coding unit is 4N×4N), the imagedecoding apparatus 100 may determine the block shape information of thecoding unit as a square. The image decoding apparatus 100 may determinethe shape of the coding unit to be a non-square.

When the width and the height of the coding unit are different from eachother (i.e., when the block shape of the coding unit is 4N×2N, 2N×4N,4N×N, N×4N, 32N×N, N×32N, 16N×N, N×16N, 8N×N, or N×8N), the imagedecoding apparatus 100 may determine the block shape information of thecoding unit as a non-square shape. When the shape of the coding unit isnon-square, the image decoding apparatus 100 may determine the ratio ofthe width and height in the block shape information of the coding unitto be at least one of 1:2, 2:1, 1:4, 4:1, 1:8, 8:1, 1:16, 16:1, 1:32,and 32:1. Also, the image decoding apparatus 100 may determine whetherthe coding unit is in a horizontal direction or a vertical direction,based on the length of the width and the length of the height of thecoding unit. Also, the image decoding apparatus 100 may determine thesize of the coding unit, based on at least one of the length of thewidth, the length of the height, or the area of the coding unit.

According to an embodiment, the image decoding apparatus 100 maydetermine the shape of the coding unit by using the block shapeinformation, and may determine a splitting method of the coding unit byusing the split shape mode information. That is, a coding unit splittingmethod indicated by the split shape mode information may be determinedbased on a block shape indicated by the block shape information used bythe image decoding apparatus 100.

The image decoding apparatus 100 may obtain the split shape modeinformation from a bitstream. However, an embodiment is not limitedthereto, and the image decoding apparatus 100 and the image encodingapparatus 2200 may determine pre-agreed split shape mode information,based on the block shape information. The image decoding apparatus 100may determine the pre-agreed split shape mode information with respectto a largest coding unit or a smallest coding unit. For example, theimage decoding apparatus 100 may determine split shape mode informationwith respect to the largest coding unit to be a quad split. Also, theimage decoding apparatus 100 may determine split shape mode informationregarding the smallest coding unit to be “not to perform splitting”. Inparticular, the image decoding apparatus 100 may determine the size ofthe largest coding unit to be 256×256. The image decoding apparatus 100may determine the pre-agreed split shape mode information to be a quadsplit. The quad split is a split shape mode in which the width and theheight of the coding unit are both bisected. The image decodingapparatus 100 may obtain a coding unit of a 128×128 size from thelargest coding unit of a 256×256 size, based on the split shape modeinformation. Also, the image decoding apparatus 100 may determine thesize of the smallest coding unit to be 4×4. The image decoding apparatus100 may obtain split shape mode information indicating “not to performsplitting” with respect to the smallest coding unit.

According to an embodiment, the image decoding apparatus 100 may use theblock shape information indicating that the current coding unit has asquare shape. For example, the image decoding apparatus 100 maydetermine whether not to split a square coding unit, whether tovertically split the square coding unit, whether to horizontally splitthe square coding unit, or whether to split the square coding unit intofour coding units, based on the split shape mode information. Referringto FIG. 3, when the block shape information of a current coding unit 300indicates a square shape, the decoder 120 may determine that a codingunit 310 a having the same size as the current coding unit 300 is notsplit, based on the split shape mode information indicating not toperform splitting, or may determine coding units 310 b, 310 c, 310 d,310 e, 310 f, or the like which are split based on the split shape modeinformation indicating a predefined splitting method.

Referring to FIG. 3, according to an embodiment, the image decodingapparatus 100 may determine two coding units 310 b obtained by splittingthe current coding unit 300 in a vertical direction, based on the splitshape mode information indicating to perform splitting in a verticaldirection. The image decoding apparatus 100 may determine two codingunits 310 c obtained by splitting the current coding unit 300 in ahorizontal direction, based on the split shape mode informationindicating to perform splitting in a horizontal direction. The imagedecoding apparatus 100 may determine four coding units 310 d obtained bysplitting the current coding unit 300 in vertical and horizontaldirections, based on the split shape mode information indicating toperform splitting in vertical and horizontal directions.

According to an embodiment, the image decoding apparatus 100 maydetermine three coding units 310 e obtained by splitting the currentcoding unit 300 in a vertical direction, based on the split shape modeinformation indicating to perform ternary-splitting in a verticaldirection. The image decoding apparatus 100 may determine three codingunits 310 f obtained by splitting the current coding unit 300 in ahorizontal direction, based on the split shape mode informationindicating to perform ternary-splitting in a horizontal direction.However, splitting methods of the square coding unit are not limited tothe above-described methods, and the split shape mode information mayindicate various methods. Predefined splitting methods of splitting thesquare coding unit will be described in detail below in relation tovarious embodiments.

FIG. 4 illustrates a process, performed by the image decoding apparatus,of determining at least one coding unit by splitting a non-square codingunit, according to an embodiment.

According to an embodiment, the image decoding apparatus 100 may useblock shape information indicating that a current coding unit has anon-square shape. The image decoding apparatus 100 may determine whethernot to split the non-square current coding unit or whether to split thenon-square current coding unit by using a predefined splitting method,based on split shape mode information. Referring to FIG. 4, when theblock shape information of a current coding unit 400 or 450 indicates anon-square shape, the image decoding apparatus 100 may determine that acoding unit 410 or 460 having the same size as the current coding unit400 or 450 is not split, based on the split shape mode informationindicating not to perform splitting, or determine coding units 420 a and420 b, 430 a to 430 c, 470 a and 470 b, or 480 a to 480 c split based onthe split shape mode information indicating a predefined splittingmethod. Predefined splitting methods of splitting a non-square codingunit will be described in detail below in relation to variousembodiments.

According to an embodiment, the image decoding apparatus 100 maydetermine a splitting method of a coding unit by using the split shapemode information and, in this case, the split shape mode information mayindicate the number of one or more coding units generated by splitting acoding unit. Referring to FIG. 4, when the split shape mode informationindicates to split the current coding unit 400 or 450 into two codingunits, the image decoding apparatus 100 may determine two coding units420 a and 420 b, or 470 a and 470 b included in the current coding unit400 or 450, by splitting the current coding unit 400 or 450 based on thesplit shape mode information.

According to an embodiment, when the image decoding apparatus 100 splitsthe non-square current coding unit 400 or 450 based on the split shapemode information, the image decoding apparatus 100 may consider thelocation of a long side of the non-square current coding unit 400 or 450to split a current coding unit. For example, the image decodingapparatus 100 may determine a plurality of coding units by splitting along side of the current coding unit 400 or 450, in consideration of theshape of the current coding unit 400 or 450.

According to an embodiment, when the split shape mode informationindicates to split (ternary-split) a coding unit into an odd number ofblocks, the image decoding apparatus 100 may determine an odd number ofcoding units included in the current coding unit 400 or 450. Forexample, when the split shape mode information indicates to split thecurrent coding unit 400 or 450 into three coding units, the imagedecoding apparatus 100 may split the current coding unit 400 or 450 intothree coding units 430 a, 430 b, and 430 c, or 480 a, 480 b, and 480 c.

According to an embodiment, a ratio of the width and height of thecurrent coding unit 400 or 450 may be 4:1 or 1:4. When the ratio of thewidth and height is 4:1, the block shape information may be a horizontaldirection because the length of the width is longer than the length ofthe height. When the ratio of the width and height is 1:4, the blockshape information may be a vertical direction because the length of thewidth is shorter than the length of the height. The image decodingapparatus 100 may determine to split a current coding unit into the oddnumber of blocks, based on the split shape mode information. Also, theimage decoding apparatus 100 may determine a split direction of thecurrent coding unit 400 or 450, based on the block shape information ofthe current coding unit 400 or 450. For example, when the current codingunit 400 is in the vertical direction, the image decoding apparatus 100may determine the coding units 430 a to 430 c by splitting the currentcoding unit 400 in the horizontal direction. Also, when the currentcoding unit 450 is in the horizontal direction, the image decodingapparatus 100 may determine the coding units 480 a to 480 c by splittingthe current coding unit 450 in the vertical direction.

According to an embodiment, the image decoding apparatus 100 maydetermine the odd number of coding units included in the current codingunit 400 or 450, and not all the determined coding units may have thesame size. For example, a predefined coding unit 430 b or 480 b fromamong the determined odd number of coding units 430 a, 430 b, and 430 c,or 480 a, 480 b, and 480 c may have a size different from the size ofthe other coding units 430 a and 430 c, or 480 a and 480 c. That is,coding units which may be determined by splitting the current codingunit 400 or 450 may have multiple sizes and, in some cases, all of theodd number of coding units 430 a, 430 b, and 430 c, or 480 a, 480 b, and480 c may have different sizes.

According to an embodiment, when the split shape mode informationindicates to split a coding unit into the odd number of blocks, theimage decoding apparatus 100 may determine the odd number of codingunits included in the current coding unit 400 or 450, and in addition,may put a predefined restriction on at least one coding unit from amongthe odd number of coding units generated by splitting the current codingunit 400 or 450. Referring to FIG. 4, the image decoding apparatus 100may allow a decoding process of the coding unit 430 b or 480 b to bedifferent from that of the other coding units 430 a and 430 c, or 480 aor 480 c, wherein the coding unit 430 b or 480 b is at a center locationfrom among the three coding units 430 a, 430 b, and 430 c or 480 a, 480b, and 480 c generated by splitting the current coding unit 400 or 450.For example, the image decoding apparatus 100 may restrict the codingunit 430 b or 480 b at the center location to be no longer split or tobe split only a predefined number of times, unlike the other codingunits 430 a and 430 c, or 480 a and 480 c.

FIG. 5 illustrates a process, performed by the image decoding apparatus,of splitting a coding unit based on at least one of block shapeinformation and split shape mode information, according to anembodiment.

According to an embodiment, the image decoding apparatus 100 maydetermine to split or not to split a square first coding unit 500 intocoding units, based on at least one of the block shape information andthe split shape mode information. According to an embodiment, when thesplit shape mode information indicates to split the first coding unit500 in a horizontal direction, the image decoding apparatus 100 maydetermine a second coding unit 510 by splitting the first coding unit500 in a horizontal direction. A first coding unit, a second codingunit, and a third coding unit used according to an embodiment are termsused to understand a relation before and after splitting a coding unit.For example, a second coding unit may be determined by splitting a firstcoding unit, and a third coding unit may be determined by splitting thesecond coding unit. It will be understood that the structure of thefirst coding unit, the second coding unit, and the third coding unitfollows the above descriptions.

According to an embodiment, the image decoding apparatus 100 maydetermine to split or not to split the determined second coding unit 510into coding units, based on the split shape mode information. Referringto FIG. 5, the image decoding apparatus 100 may split the non-squaresecond coding unit 510, which is determined by splitting the firstcoding unit 500, into one or more third coding units 520 a, or 520 b,520 c, and 520 d based on the split shape mode information, or may notsplit the non-square second coding unit 510. The image decodingapparatus 100 may obtain the split shape mode information, and mayobtain a plurality of various-shaped second coding units (e.g., 510) bysplitting the first coding unit 500, based on the obtained split shapemode information, and the second coding unit 510 may be split by using asplitting method of the first coding unit 500 based on the split shapemode information. According to an embodiment, when the first coding unit500 is split into the second coding units 510 based on the split shapemode information of the first coding unit 500, the second coding unit510 may also be split into the third coding units 520 a, or 520 b, 520c, and 520 d based on the split shape mode information of the secondcoding unit 510. That is, a coding unit may be recursively split basedon the split shape mode information of each coding unit. Therefore, asquare coding unit may be determined by splitting a non-square codingunit, and a non-square coding unit may be determined by recursivelysplitting the square coding unit.

Referring to FIG. 5, a predefined coding unit from among the odd numberof third coding units 520 b, 520 c, and 520 d determined by splittingthe non-square second coding unit 510 (e.g., a coding unit or a squarecoding unit, which is located at a center location) may be recursivelysplit. According to an embodiment, the square third coding unit 520 cfrom among the odd number of third coding units 520 b, 520 c, and 520 dmay be split in a horizontal direction into a plurality of fourth codingunits. A non-square fourth coding unit 530 b or 530 d from among aplurality of fourth coding units 530 a, 530 b, 530 c, and 530 d may besplit into a plurality of coding units again. For example, thenon-square fourth coding unit 530 b or 530 d may be split into the oddnumber of coding units again. A method that may be used to recursivelysplit a coding unit will be described below in relation to variousembodiments.

According to an embodiment, the image decoding apparatus 100 may spliteach of the third coding units 520 a, or 520 b, 520 c, and 520 d intocoding units, based on the split shape mode information. Also, the imagedecoding apparatus 100 may determine not to split the second coding unit510 based on the split shape mode information. According to anembodiment, the image decoding apparatus 100 may split the non-squaresecond coding unit 510 into the odd number of third coding units 520 b,520 c, and 520 d. The image decoding apparatus 100 may put a predefinedrestriction on a predefined third coding unit from among the odd numberof third coding units 520 b, 520 c, and 520 d. For example, the imagedecoding apparatus 100 may restrict the third coding unit 520 c at acenter location from among the odd number of third coding units 520 b,520 c, and 520 d to be no longer split or to be split a settable numberof times.

Referring to FIG. 5, the image decoding apparatus 100 may restrict thethird coding unit 520 c, which is at the center location from among theodd number of third coding units 520 b, 520 c, and 520 d included in thenon-square second coding unit 510, to be no longer split, to be split byusing a predefined splitting method (e.g., split into only four codingunits or split by using a splitting method of the second coding unit510), or to be split only a predefined number of times (e.g., split onlyn times (where n>0)). However, the restrictions on the third coding unit520 c at the center location are not limited to the above-describedexamples, and may include various restrictions for decoding the thirdcoding unit 520 c at the center location differently from the otherthird coding units 520 b and 520 d.

According to an embodiment, the image decoding apparatus 100 may obtainthe split shape mode information, which is used to split a currentcoding unit, from a predefined location in the current coding unit.

FIG. 6 illustrates a method, performed by the image decoding apparatus,of determining a predefined coding unit from among an odd number ofcoding units, according to an embodiment.

Referring to FIG. 6, split shape mode information of a current codingunit 600 or 650 may be obtained from a sample of a predefined location(e.g., a sample 640 or 690 of a center location) from among a pluralityof samples included in the current coding unit 600 or 650. However, thepredefined location in the current coding unit 600, from which at leastone piece of the split shape mode information may be obtained, is notlimited to the center location in FIG. 6, and may include variouslocations included in the current coding unit 600 (e.g., top, bottom,left, right, upper left, lower left, upper right, and lower rightlocations). The image decoding apparatus 100 may obtain the split shapemode information from the predefined location and may determine to splitor not to split the current coding unit into various-shaped andvarious-sized coding units.

According to an embodiment, when the current coding unit is split into apredefined number of coding units, the image decoding apparatus 100 mayselect one of the coding units. Various methods may be used to selectone of a plurality of coding units, as will be described below inrelation to various embodiments.

According to an embodiment, the image decoding apparatus 100 may splitthe current coding unit into a plurality of coding units, and maydetermine a coding unit at a predefined location.

According to an embodiment, image decoding apparatus 100 may useinformation indicating locations of the odd number of coding units, todetermine a coding unit at a center location from among the odd numberof coding units. Referring to FIG. 6, the image decoding apparatus 100may determine the odd number of coding units 620 a, 620 b, and 620 c orthe odd number of coding units 660 a, 660 b, and 660 c by splitting thecurrent coding unit 600 or the current coding unit 650. The imagedecoding apparatus 100 may determine the middle coding unit 620 b or themiddle coding unit 660 b by using information about the locations of theodd number of coding units 620 a, 620 b, and 620 c or the odd number ofcoding units 660 a, 660 b, and 660 c. For example, the image decodingapparatus 100 may determine the coding unit 620 b of the center locationby determining the locations of the coding units 620 a, 620 b, and 620 cbased on information indicating locations of predefined samples includedin the coding units 620 a, 620 b, and 620 c. In detail, the imagedecoding apparatus 100 may determine the coding unit 620 b at the centerlocation by determining the locations of the coding units 620 a, 620 b,and 620 c based on information indicating locations of upper leftsamples 630 a, 630 b, and 630 c of the coding units 620 a, 620 b, and620 c.

According to an embodiment, the information indicating the locations ofthe upper left samples 630 a, 630 b, and 630 c, which are included inthe coding units 620 a, 620 b, and 620 c, respectively, may includeinformation about locations or coordinates of the coding units 620 a,620 b, and 620 c in a picture. According to an embodiment, theinformation indicating the locations of the upper left samples 630 a,630 b, and 630 c, which are included in the coding units 620 a, 620 b,and 620 c, respectively, may include information indicating widths orheights of the coding units 620 a, 620 b, and 620 c included in thecurrent coding unit 600, and the widths or heights may correspond toinformation indicating differences between the coordinates of the codingunits 620 a, 620 b, and 620 c in the picture. That is, the imagedecoding apparatus 100 may determine the coding unit 620 b at the centerlocation by directly using the information about the locations orcoordinates of the coding units 620 a, 620 b, and 620 c in the picture,or by using the information about the widths or heights of the codingunits, which correspond to the difference values between thecoordinates.

According to an embodiment, information indicating the location of theupper left sample 630 a of the upper coding unit 620 a may includecoordinates (xa, ya), information indicating the location of the upperleft sample 630 b of the middle coding unit 620 b may includecoordinates (xb, yb), and information indicating the location of theupper left sample 630 c of the lower coding unit 620 c may includecoordinates (xc, yc). The image decoding apparatus 100 may determine themiddle coding unit 620 b by using the coordinates of the upper leftsamples 630 a, 630 b, and 630 c which are included in the coding units620 a, 620 b, and 620 c, respectively. For example, when the coordinatesof the upper left samples 630 a, 630 b, and 630 c are sorted in anascending or descending order, the coding unit 620 b including thecoordinates (xb, yb) of the sample 630 b at a center location may bedetermined as a coding unit at a center location from among the codingunits 620 a, 620 b, and 620 c determined by splitting the current codingunit 600. However, the coordinates indicating the locations of the upperleft samples 630 a, 630 b, and 630 c may include coordinates indicatingabsolute locations in the picture, or may use coordinates (dxb, dyb)indicating a relative location of the upper left sample 630 b of themiddle coding unit 620 b and coordinates (dxc, dyc) indicating arelative location of the upper left sample 630 c of the lower codingunit 620 c with reference to the location of the upper left sample 630 aof the upper coding unit 620 a. A method of determining a coding unit ata predefined location by using coordinates of a sample included in thecoding unit, as information indicating a location of the sample, is notlimited to the above-described method, and may include variousarithmetic methods capable of using the coordinates of the sample.

According to an embodiment, the image decoding apparatus 100 may splitthe current coding unit 600 into a plurality of coding units 620 a, 620b, and 620 c, and may select one of the coding units 620 a, 620 b, and620 c based on a predefined criterion. For example, the image decodingapparatus 100 may select the coding unit 620 b, which has a sizedifferent from that of the others, from among the coding units 620 a,620 b, and 620 c.

According to an embodiment, the image decoding apparatus 100 maydetermine the width or height of each of the coding units 620 a, 620 b,and 620 c by using the coordinates (xa, ya) that is the informationindicating the location of the upper left sample 630 a of the uppercoding unit 620 a, the coordinates (xb, yb) that is the informationindicating the location of the upper left sample 630 b of the middlecoding unit 620 b, and the coordinates (xc, yc) that is the informationindicating the location of the upper left sample 630 c of the lowercoding unit 620 c. The image decoding apparatus 100 may determine therespective sizes of the coding units 620 a, 620 b, and 620 c by usingthe coordinates (xa, ya), (xb, yb), and (xc, yc) indicating thelocations of the coding units 620 a, 620 b, and 620 c. According to anembodiment, the image decoding apparatus 100 may determine the width ofthe upper coding unit 620 a to be the width of the current coding unit600. The image decoding apparatus 100 may determine the height of theupper coding unit 620 a to be yb−ya. According to an embodiment, theimage decoding apparatus 100 may determine the width of the middlecoding unit 620 b to be the width of the current coding unit 600. Theimage decoding apparatus 100 may determine the height of the middlecoding unit 620 b to be yc−yb. According to an embodiment, the imagedecoding apparatus 100 may determine the width or height of the lowercoding unit 620 c by using the width or height of the current codingunit 600 or the widths or heights of the upper and middle coding units620 a and 620 b. The image decoding apparatus 100 may determine a codingunit, which has a size different from that of the others, based on thedetermined widths and heights of the coding units 620 a to 620 c.Referring to FIG. 6, the image decoding apparatus 100 may determine themiddle coding unit 620 b, which has a size different from the size ofthe upper and lower coding units 620 a and 620 c, as the coding unit ofthe predefined location. However, the above-described method, performedby the image decoding apparatus 100, of determining a coding unit havinga size different from the size of the other coding units merelycorresponds to an example of determining a coding unit at a predefinedlocation by using the sizes of coding units, which are determined basedon coordinates of samples, and thus various methods of determining acoding unit at a predefined location by comparing the sizes of codingunits, which are determined based on coordinates of predefined samples,may be used.

The image decoding apparatus 100 may determine the width or height ofeach of the coding units 660 a, 660 b, and 660 c by using thecoordinates (xd, yd) that is information indicating the location of aupper left sample 670 a of the left coding unit 660 a, the coordinates(xe, ye) that is information indicating the location of a upper leftsample 670 b of the middle coding unit 660 b, and the coordinates (xf,yf) that is information indicating a location of the upper left sample670 c of the right coding unit 660 c. The image decoding apparatus 100may determine the respective sizes of the coding units 660 a, 660 b, and660 c by using the coordinates (xd, yd), (xe, ye), and (xf, yf)indicating the locations of the coding units 660 a, 660 b, and 660 c.

According to an embodiment, the image decoding apparatus 100 maydetermine the width of the left coding unit 660 a to be xe−xd. The imagedecoding apparatus 100 may determine the height of the left coding unit660 a to be the height of the current coding unit 650. According to anembodiment, the image decoding apparatus 100 may determine the width ofthe middle coding unit 660 b to be xf−xe. The image decoding apparatus100 may determine the height of the middle coding unit 660 b to be theheight of the current coding unit 650. According to an embodiment, theimage decoding apparatus 100 may determine the width or height of theright coding unit 660 c by using the width or height of the currentcoding unit 650 or the widths or heights of the left and middle codingunits 660 a and 660 b. The image decoding apparatus 100 may determine acoding unit, which has a size different from that of the others, basedon the determined widths and heights of the coding units 660 a to 660 c.Referring to FIG. 6, the image decoding apparatus 100 may determine themiddle coding unit 660 b, which has a size different from the sizes ofthe left and right coding units 660 a and 660 c, as the coding unit ofthe predefined location. However, the above-described method, performedby the image decoding apparatus 100, of determining a coding unit havinga size different from the size of the other coding units merelycorresponds to an example of determining a coding unit at a predefinedlocation by using the sizes of coding units, which are determined basedon coordinates of samples, and thus various methods of determining acoding unit at a predefined location by comparing the sizes of codingunits, which are determined based on coordinates of predefined samples,may be used.

However, locations of samples considered to determine locations ofcoding units are not limited to the above-described upper leftlocations, and information about arbitrary locations of samples includedin the coding units may be used.

According to an embodiment, the image decoding apparatus 100 may selecta coding unit at a predefined location from among an odd number ofcoding units determined by splitting the current coding unit, inconsideration the shape of the current coding unit. For example, whenthe current coding unit has a non-square shape, a width of which islonger than a height, the image decoding apparatus 100 may determine thecoding unit at the predefined location in a horizontal direction. Thatis, the image decoding apparatus 100 may determine one of coding unitsat different locations in a horizontal direction and may put arestriction on the coding unit. When the current coding unit has anon-square shape, a height of which is longer than a width, the imagedecoding apparatus 100 may determine the coding unit at the predefinedlocation in a vertical direction. That is, the image decoding apparatus100 may determine one of coding units at different locations in avertical direction and may put a restriction on the coding unit.

According to an embodiment, the image decoding apparatus 100 may useinformation indicating respective locations of an even number of codingunits, to determine the coding unit at the predefined location fromamong the even number of coding units. The image decoding apparatus 100may determine an even number of coding units by splitting(binary-splitting) the current coding unit, and may determine the codingunit at the predefined location by using the information about thelocations of the even number of coding units. An operation relatedthereto may correspond to the operation of determining a coding unit ata predefined location (e.g., a center location) from among an odd numberof coding units, which has been described in detail above in relation toFIG. 6, and thus detailed descriptions thereof are not provided here.

According to an embodiment, when a non-square current coding unit issplit into a plurality of coding units, predefined information about acoding unit at a predefined location may be used in a splittingoperation to determine the coding unit at the predefined location fromamong the plurality of coding units. For example, the image decodingapparatus 100 may use at least one of block shape information and splitshape mode information, which is stored in a sample included in a middlecoding unit, in a splitting operation to determine a coding unit at acenter location from among the plurality of coding units determined bysplitting the current coding unit.

Referring to FIG. 6, the image decoding apparatus 100 may split thecurrent coding unit 600 into the plurality of coding units 620 a, 620 b,and 620 c based on the split shape mode information, and may determinethe coding unit 620 b at a center location from among the plurality ofthe coding units 620 a, 620 b, and 620 c. Furthermore, the imagedecoding apparatus 100 may determine the coding unit 620 b at the centerlocation, in consideration of a location from which the split shape modeinformation is obtained. That is, the split shape mode information ofthe current coding unit 600 may be obtained from the sample 640 at acenter location of the current coding unit 600 and, when the currentcoding unit 600 is split into the plurality of coding units 620 a, 620b, and 620 c based on the split shape mode information, the coding unit620 b including the sample 640 may be determined as the coding unit atthe center location. However, information used to determine the codingunit at the center location is not limited to the split shape modeinformation, and various types of information may be used to determinethe coding unit at the center location.

According to an embodiment, predefined information for identifying thecoding unit at the predefined location may be obtained from a predefinedsample included in a coding unit to be determined. Referring to FIG. 6,the image decoding apparatus 100 may use the split shape modeinformation, which is obtained from a sample at a predefined location inthe current coding unit 600 (e.g., a sample at a center location of thecurrent coding unit 600) to determine a coding unit at a predefinedlocation from among the plurality of the coding units 620 a, 620 b, and620 c determined by splitting the current coding unit 600 (e.g., acoding unit at a center location from among a plurality of split codingunits). That is, the image decoding apparatus 100 may determine thesample at the predefined location by considering a block shape of thecurrent coding unit 600, may determine the coding unit 620 b including asample, from which predefined information (e.g., the split shape modeinformation) is obtainable, from among the plurality of coding units 620a, 620 b, and 620 c determined by splitting the current coding unit 600,and may put a predefined restriction on the coding unit 620 b. Referringto FIG. 6, according to an embodiment, the image decoding apparatus 100may determine the sample 640 at the center location of the currentcoding unit 600 as the sample from which the predefined information maybe obtained, and may put a predefined restriction on the coding unit 620b including the sample 640, in a decoding operation. However, thelocation of the sample from which the predefined information isobtainable is not limited to the above-described location, and mayinclude arbitrary locations of samples included in the coding unit 620 bto be determined for a restriction.

According to an embodiment, the location of the sample from which thepredefined information is obtainable may be determined based on theshape of the current coding unit 600. According to an embodiment, theblock shape information may indicate whether the current coding unit hasa square or non-square shape, and the location of the sample from whichthe predefined information is obtainable may be determined based on theshape. For example, the image decoding apparatus 100 may determine asample located on a boundary for splitting at least one of a width andheight of the current coding unit in half, as the sample from which thepredefined information is obtainable, by using at least one ofinformation about the width of the current coding unit and informationabout the height of the current coding unit. As another example, whenthe block shape information of the current coding unit indicates anon-square shape, the image decoding apparatus 100 may determine one ofsamples adjacent to a boundary for splitting a long side of the currentcoding unit in half, as the sample from which the predefined informationis obtainable.

According to an embodiment, when the current coding unit is split into aplurality of coding units, the image decoding apparatus 100 may use thesplit shape mode information to determine a coding unit at a predefinedlocation from among the plurality of coding units. According to anembodiment, the image decoding apparatus 100 may obtain the split shapemode information from a sample at a predefined location in a codingunit, and may split the plurality of coding units, which are generatedby splitting the current coding unit, by using the split shape modeinformation, which is obtained from the sample of the predefinedlocation in each of the plurality of coding units. That is, a codingunit may be recursively split based on the split shape mode information,which is obtained from the sample at the predefined location in eachcoding unit. An operation of recursively splitting a coding unit hasbeen described above in relation to FIG. 5, and thus detaileddescriptions thereof will not be provided here.

According to an embodiment, the image decoding apparatus 100 maydetermine one or more coding units by splitting the current coding unit,and may determine an order of decoding the one or more coding units,based on a predefined block (e.g., the current coding unit).

FIG. 7 illustrates an order of processing a plurality of coding unitswhen the image decoding apparatus determines the plurality of codingunits by splitting a current coding unit, according to an embodiment.

According to an embodiment, the image decoding apparatus 100 maydetermine second coding units 710 a and 710 b by splitting a firstcoding unit 700 in a vertical direction, may determine second codingunits 730 a and 730 b by splitting the first coding unit 700 in ahorizontal direction, or may determine second coding units 750 a to 750d by splitting the first coding unit 700 in vertical and horizontaldirections, based on split shape mode information.

Referring to FIG. 7, the image decoding apparatus 100 may determine toprocess the second coding units 710 a and 710 b, which are determined bysplitting the first coding unit 700 in a vertical direction, in ahorizontal direction order 710 c. The image decoding apparatus 100 maydetermine to process the second coding units 730 a and 730 b, which aredetermined by splitting the first coding unit 700 in a horizontaldirection, in a vertical direction order 730 c. The image decodingapparatus 100 may determine to process the second coding units 750 a to750 d, which are determined by splitting the first coding unit 700 invertical and horizontal directions, according to a predefined order(e.g., a raster scan order or Z-scan order 750 e) by which coding unitsin a row are processed and then coding units in a next row areprocessed.

According to an embodiment, the image decoding apparatus 100 mayrecursively split coding units. Referring to FIG. 7, the image decodingapparatus 100 may determine the plurality of coding units 710 a and 710b, 730 a and 730 b, or 750 a, 750 b, 750 c, and 750 d by splitting thefirst coding unit 700, and may recursively split each of the determinedplurality of coding units 710 a and 710 b, 730 a and 730 b, or 750 a,750 b, 750 c, and 750 d. A splitting method of the plurality of codingunits 710 a and 710 b, 730 a and 730 b, or 750 a, 750 b, 750 c, and 750d may correspond to a splitting method of the first coding unit 700. Assuch, each of the plurality of coding units 710 a and 710 b, 730 a and730 b, or 750 a, 750 b, 750 c, and 750 d may be independently split intoa plurality of coding units. Referring to FIG. 7, the image decodingapparatus 100 may determine the second coding units 710 a and 710 b bysplitting the first coding unit 700 in a vertical direction, and maydetermine to independently split or not to split each of the secondcoding units 710 a and 710 b.

According to an embodiment, the image decoding apparatus 100 maydetermine third coding units 720 a and 720 b by splitting the leftsecond coding unit 710 a in a horizontal direction, and may not splitthe right second coding unit 710 b.

According to an embodiment, a processing order of coding units may bedetermined based on an operation of splitting a coding unit. In otherwords, a processing order of split coding units may be determined basedon a processing order of coding units immediately before being split.The image decoding apparatus 100 may determine a processing order of thethird coding units 720 a and 720 b determined by splitting the leftsecond coding unit 710 a, independently of the right second coding unit710 b. Because the third coding units 720 a and 720 b are determined bysplitting the left second coding unit 710 a in a horizontal direction,the third coding units 720 a and 720 b may be processed in a verticaldirection order 720 c. Because the left and right second coding units710 a and 710 b are processed in the horizontal direction order 710 c,the right second coding unit 710 b may be processed after the thirdcoding units 720 a and 720 b included in the left second coding unit 710a are processed in the vertical direction order 720 c. An operation ofdetermining a processing order of coding units based on a coding unitbefore being split is not limited to the above-described example, andvarious methods may be used to independently process coding units, whichare split and determined to various shapes, in a predefined order.

FIG. 8 illustrates a process, performed by the image decoding apparatus,of determining that a current coding unit is to be split into an oddnumber of coding units, when the coding units are not processable in apredefined order, according to an embodiment.

According to an embodiment, the image decoding apparatus 100 maydetermine that the current coding unit is to be split into an odd numberof coding units, based on obtained split shape mode information.Referring to FIG. 8, a square first coding unit 800 may be split intonon-square second coding units 810 a and 810 b, and the second codingunits 810 a and 810 b may be independently split into third coding units820 a and 820 b, and 820 c, 820 d, and 820 e. According to anembodiment, the image decoding apparatus 100 may determine the pluralityof third coding units 820 a and 820 b by splitting the left secondcoding unit 810 a in a horizontal direction, and may split the rightsecond coding unit 810 b into the odd number of third coding units 820c, 820 d, and 820 e.

According to an embodiment, the image decoding apparatus 100 maydetermine whether any coding unit that is split into an odd number ofcoding units exists, by determining whether the third coding units 820 aand 820 b, and 820 c, 820 d, and 820 e are processable in a predefinedorder. Referring to FIG. 8, the image decoding apparatus 100 maydetermine the third coding units 820 a and 820 b, and 820 c, 820 d, and820 e by recursively splitting the first coding unit 800. The imagedecoding apparatus 100 may determine whether any of the first codingunit 800, the second coding units 810 a and 810 b, and the third codingunits 820 a and 820 b, and 820 c, 820 d, and 820 e are to be split intoan odd number of coding units, based on at least one of the block shapeinformation and the split shape mode information. For example, thesecond coding unit 810 b located in the right from among the secondcoding units 810 a and 810 b may be split into an odd number of thirdcoding units 820 c, 820 d, and 820 e. A processing order of a pluralityof coding units included in the first coding unit 800 may be apredefined order (e.g., a Z-scan order 830), and the image decodingapparatus 100 may determine whether the third coding units 820 c, 820 d,and 820 e, which are determined by splitting the right second codingunit 810 b into an odd number of coding units, satisfy a condition forprocessing in the predefined order.

According to an embodiment, the image decoding apparatus 100 maydetermine whether the third coding units 820 a and 820 b, and 820 c, 820d, and 820 e included in the first coding unit 800 satisfy the conditionfor processing in the predefined order, and the condition relates towhether at least one of a width and height of the second coding units810 a and 810 b is to be split in half along a boundary of the thirdcoding units 820 a and 820 b, and 820 c, 820 d, and 820 e. For example,the third coding units 820 a and 820 b determined when the height of theleft second coding unit 810 a of the non-square shape is split in halfmay satisfy the condition. It may be determined that the third codingunits 820 c to 820 e do not satisfy the condition because the boundariesof the third coding units 820 c to 820 e determined when the rightsecond coding unit 810 b is split into three coding units are unable tosplit the width or height of the right second coding unit 810 b in half.When the condition is not satisfied as described above, the imagedecoding apparatus 100 may determine disconnection of a scan order, andmay determine that the right second coding unit 810 b is to be splitinto an odd number of coding units, based on a result of thedetermination. According to an embodiment, when a coding unit is splitinto an odd number of coding units, the image decoding apparatus 100 mayput a predefined restriction on a coding unit at a predefined locationfrom among the split coding units. The restriction or the predefinedlocation has been described above in relation to various embodiments,and thus detailed descriptions thereof will not be provided herein.

FIG. 9 illustrates a process, performed by the image decoding apparatus,of determining at least one coding unit by splitting a first codingunit, according to an embodiment.

According to an embodiment, the image decoding apparatus 100 may split afirst coding unit 900, based on split shape mode information which isobtained through the receiver 110. The square first coding unit 900 maybe split into four square coding units, or may be split into a pluralityof non-square coding units. For example, referring to FIG. 9, when thefirst coding unit 900 has a square shape and the split shape modeinformation indicates to split the first coding unit 900 into non-squarecoding units, the image decoding apparatus 100 may split the firstcoding unit 900 into a plurality of non-square coding units. In detail,when the split shape mode information indicates to determine an oddnumber of coding units by splitting the first coding unit 900 in ahorizontal direction or a vertical direction, the image decodingapparatus 100 may split the square first coding unit 900 into an oddnumber of coding units, e.g., second coding units 910 a, 910 b, and 910c determined by splitting the square first coding unit 900 in a verticaldirection or second coding units 920 a, 920 b, and 920 c determined bysplitting the square first coding unit 900 in a horizontal direction.

According to an embodiment, the image decoding apparatus 100 maydetermine whether the second coding units 910 a, 910 b, 910 c, 920 a,920 b, and 920 c included in the first coding unit 900 satisfy acondition for processing in a predefined order, and the conditionrelates to whether at least one of a width and height of the firstcoding unit 900 is to be split in half along a boundary of the secondcoding units 910 a, 910 b, 910 c, 920 a, 920 b, and 920 c. Referring toFIG. 9, because boundaries of the second coding units 910 a, 910 b, and910 c determined by splitting the square first coding unit 900 in avertical direction do not split the width of the first coding unit 900in half, it may be determined that the first coding unit 900 does notsatisfy the condition for processing in the predefined order. Inaddition, because boundaries of the second coding units 920 a, 920 b,and 920 c determined by splitting the square first coding unit 900 in ahorizontal direction do not split the width of the first coding unit 900in half, it may be determined that the first coding unit 900 does notsatisfy the condition for processing in the predefined order. When thecondition is not satisfied as described above, the image decodingapparatus 100 may decide disconnection of a scan order, and maydetermine that the first coding unit 900 is to be split into an oddnumber of coding units, based on a result of the decision. According toan embodiment, when a coding unit is split into an odd number of codingunits, the image decoding apparatus 100 may put a predefined restrictionon a coding unit at a predefined location from among the split codingunits. The restriction or the predefined location has been describedabove with reference to various embodiments, and thus detaileddescriptions thereof will not be provided herein.

According to an embodiment, the image decoding apparatus 100 maydetermine various-shaped coding units by splitting a first coding unit.

Referring to FIG. 9, the image decoding apparatus 100 may split thesquare first coding unit 900 or a non-square first coding unit 930 or950 into various-shaped coding units.

FIG. 10 illustrates that a shape into which a second coding unit issplittable is restricted when the second coding unit having a non-squareshape, which is determined as the image decoding apparatus 100 splits afirst coding unit 1000, satisfies a predefined condition, according toan embodiment.

According to an embodiment, the image decoding apparatus 100 maydetermine to split the square first coding unit 1000 into non-squaresecond coding units 1010 a and 1010 b or 1020 a and 1020 b, based onsplit shape mode information, which is obtained by the receiver 110. Thesecond coding units 1010 a and 1010 b or 1020 a and 1020 b may beindependently split. Accordingly, the image decoding apparatus 100 maydetermine to split or not to split each of the second coding units 1010a and 1010 b or 1020 a and 1020 b into a plurality of coding units,based on the split shape mode information of each of the second codingunits 1010 a and 1010 b or 1020 a and 1020 b. According to anembodiment, the image decoding apparatus 100 may determine third codingunits 1012 a and 1012 b by splitting the non-square left second codingunit 1010 a, which is determined by splitting the first coding unit 1000in a vertical direction, in a horizontal direction. However, when theleft second coding unit 1010 a is split in a horizontal direction, theimage decoding apparatus 100 may restrict the right second coding unit1010 b to not be split in a horizontal direction in which the leftsecond coding unit 1010 a is split. When third coding units 1014 a and1014 b are determined by splitting the right second coding unit 1010 bin a same direction, because the left and right second coding units 1010a and 1010 b are independently split in a horizontal direction, thethird coding units 1012 a and 1012 b or 1014 a and 1014 b may bedetermined. However, this case serves equally as a case in which theimage decoding apparatus 100 splits the first coding unit 1000 into foursquare second coding units 1030 a, 1030 b, 1030 c, and 1030 d, based onthe split shape mode information, and may be inefficient in terms ofimage decoding.

According to an embodiment, the image decoding apparatus 100 maydetermine third coding units 1022 a and 1022 b or 1024 a and 1024 b bysplitting the non-square second coding unit 1020 a or 1020 b, which isdetermined by splitting the first coding unit 1000 in a horizontaldirection, in a vertical direction. However, when a second coding unit(e.g., the upper second coding unit 1020 a) is split in a verticaldirection, for the above-described reason, the image decoding apparatus100 may restrict the other second coding unit (e.g., the lower secondcoding unit 1020 b) to not be split in a vertical direction in which theupper second coding unit 1020 a is split.

FIG. 11 illustrates a process, performed by the image decodingapparatus, of splitting a square coding unit when split shape modeinformation is unable to indicate that the square coding unit is splitinto four square coding units, according to an embodiment.

According to an embodiment, the image decoding apparatus 100 maydetermine second coding units 1110 a and 1110 b or 1120 a and 1120 b,etc. by splitting a first coding unit 1100, based on split shape modeinformation. The split shape mode information may include informationabout various shapes in which a coding unit is splittable but, theinformation about various shapes may not include information forsplitting the coding unit into four square coding units. According tosuch split shape mode information, the image decoding apparatus 100 maynot split the square first coding unit 1100 into four square secondcoding units 1130 a, 1130 b, 1130 c, and 1130 d. The image decodingapparatus 100 may determine the non-square second coding units 1110 aand 1110 b or 1120 a and 1120 b, etc., based on the split shape modeinformation.

According to an embodiment, the image decoding apparatus 100 mayindependently split the non-square second coding units 1110 a and 1110 bor 1120 a and 1120 b, etc. Each of the second coding units 1110 a and1110 b or 1120 a and 1120 b, etc. may be recursively split in apredefined order, and this splitting method may correspond to a methodof splitting the first coding unit 1100, based on the split shape modeinformation.

For example, the image decoding apparatus 100 may determine square thirdcoding units 1112 a and 1112 b by splitting the left second coding unit1110 a in a horizontal direction, and may determine square third codingunits 1114 a and 1114 b by splitting the right second coding unit 1110 bin a horizontal direction. Furthermore, the image decoding apparatus 100may determine square third coding units 1116 a, 1116 b, 1116 c, and 1116d by splitting both of the left and right second coding units 1110 a and1110 b in a horizontal direction. In this case, coding units having thesame shape as the four square second coding units 1130 a, 1130 b, 1130c, and 1130 d split from the first coding unit 1100 may be determined.

As another example, the image decoding apparatus 100 may determinesquare third coding units 1122 a and 1122 b by splitting the uppersecond coding unit 1120 a in a vertical direction, and may determinesquare third coding units 1124 a and 1124 b by splitting the lowersecond coding unit 1120 b in a vertical direction. Furthermore, theimage decoding apparatus 100 may determine square third coding units1126 a, 1126 b, 1126 c, and 1126 d by splitting both of the upper andlower second coding units 1120 a and 1120 b in a vertical direction. Inthis case, coding units having the same shape as the four square secondcoding units 1130 a, 1130 b, 1130 c, and 1130 d split from the firstcoding unit 1100 may be determined.

FIG. 12 illustrates that a processing order of a plurality of codingunits may be changed depending on a process of splitting a coding unit,according to an embodiment.

According to an embodiment, the image decoding apparatus 100 may split afirst coding unit 1200, based on split shape mode information. When ablock shape indicates a square shape and the split shape modeinformation indicates to split the first coding unit 1200 in at leastone of horizontal and vertical directions, the image decoding apparatus100 may determine second coding units 1210 a and 1210 b or 1220 a and1220 b, etc. by splitting the first coding unit 1200. Referring to FIG.12, the non-square second coding units 1210 a and 1210 b or 1220 a and1220 b determined by splitting the first coding unit 1200 in only ahorizontal direction or vertical direction may be independently splitbased on the split shape mode information of each coding unit. Forexample, the image decoding apparatus 100 may determine third codingunits 1216 a, 1216 b, 1216 c, and 1216 d by splitting the second codingunits 1210 a and 1210 b, which are generated by splitting the firstcoding unit 1200 in a vertical direction, in a horizontal direction, andmay determine third coding units 1226 a, 1226 b, 1226 c, and 1226 d bysplitting the second coding units 1220 a and 1220 b, which are generatedby splitting the first coding unit 1200 in a horizontal direction, in ahorizontal direction. An operation of splitting the second coding units1210 a and 1210 b or 1220 a and 1220 b has been described above inrelation to FIG. 11, and thus detailed descriptions thereof will not beprovided herein.

According to an embodiment, the image decoding apparatus 100 may processcoding units in a predefined order. An operation of processing codingunits in a predefined order has been described above in relation to FIG.7, and thus detailed descriptions thereof will not be provided herein.Referring to FIG. 12, the image decoding apparatus 100 may determinefour square third coding units 1216 a, 1216 b, 1216 c, and 1216 d, and1226 a, 1226 b, 1226 c, and 1226 d by splitting the square first codingunit 1200. According to an embodiment, the image decoding apparatus 100may determine processing orders of the third coding units 1216 a, 1216b, 1216 c, and 1216 d, and 1226 a, 1226 b, 1226 c, and 1226 d based on asplitting method of the first coding unit 1200.

According to an embodiment, the image decoding apparatus 100 maydetermine the third coding units 1216 a, 1216 b, 1216 c, and 1216 d bysplitting the second coding units 1210 a and 1210 b generated bysplitting the first coding unit 1200 in a vertical direction, in ahorizontal direction, and may process the third coding units 1216 a,1216 b, 1216 c, and 1216 d in a processing order 1217 for initiallyprocessing the third coding units 1216 a and 1216 c, which are includedin the left second coding unit 1210 a, in a vertical direction and thenprocessing the third coding unit 1216 b and 1216 d, which are includedin the right second coding unit 1210 b, in a vertical direction.

According to an embodiment, the image decoding apparatus 100 maydetermine the third coding units 1226 a, 1226 b, 1226 c, and 1226 d bysplitting the second coding units 1220 a and 1220 b generated bysplitting the first coding unit 1200 in a horizontal direction, in avertical direction, and may process the third coding units 1226 a, 1226b, 1226 c, and 1226 d in a processing order 1227 for initiallyprocessing the third coding units 1226 a and 1226 b, which are includedin the upper second coding unit 1220 a, in a horizontal direction andthen processing the third coding unit 1226 c and 1226 d, which areincluded in the lower second coding unit 1220 b, in a horizontaldirection.

Referring to FIG. 12, the square third coding units 1216 a, 1216 b, 1216c, and 1216 d, and 1226 a, 1226 b, 1226 c, and 1226 d may be determinedby splitting the second coding units 1210 a and 1210 b, and 1220 a and1220 b, respectively. Although the second coding units 1210 a and 1210 bare determined by splitting the first coding unit 1200 in a verticaldirection differently from the second coding units 1220 a and 1220 bwhich are determined by splitting the first coding unit 1200 in ahorizontal direction, the third coding units 1216 a, 1216 b, 1216 c, and1216 d, and 1226 a, 1226 b, 1226 c, and 1226 d split therefromeventually illustrates same-shaped coding units split from the firstcoding unit 1200. Accordingly, by recursively splitting a coding unit indifferent manners based on the split shape mode information, the imagedecoding apparatus 100 may process a plurality of coding units indifferent orders even when the coding units are eventually determined tobe the same shape.

FIG. 13 illustrates a process of determining a depth of a coding unit asa shape and size of the coding unit change, when the coding unit isrecursively split such that a plurality of coding units are determined,according to an embodiment.

According to an embodiment, the image decoding apparatus 100 maydetermine the depth of the coding unit, based on a predefined criterion.For example, the predefined criterion may be the length of a long sideof the coding unit. When the length of a long side of a coding unitbefore being split is 2n times (n>0) the length of a long side of asplit current coding unit, the image decoding apparatus 100 maydetermine that a depth of the current coding unit is increased from adepth of the coding unit before being split, by n. In the followingdescriptions, a coding unit having an increased depth is expressed as acoding unit of a deeper depth.

Referring to FIG. 13, according to an embodiment, the image decodingapparatus 100 may determine a second coding unit 1302 and a third codingunit 1304 of deeper depths by splitting a square first coding unit 1300based on block shape information indicating a square shape (for example,the block shape information may be expressed as ‘0: SQUARE’). Assumingthat the size of the square first coding unit 1300 is 2N×2N, the secondcoding unit 1302 determined by splitting a width and height of the firstcoding unit 1300 in ½ may have a size of N×N. Furthermore, the thirdcoding unit 1304 determined by splitting a width and height of thesecond coding unit 1302 in ½ may have a size of N/2×N/2. In this case, awidth and height of the third coding unit 1304 are ¼ times those of thefirst coding unit 1300. When a depth of the first coding unit 1300 is D,a depth of the second coding unit 1302, the width and height of whichare ½ times those of the first coding unit 1300, may be D+1, and a depthof the third coding unit 1304, the width and height of which are ¼ timesthose of the first coding unit 1300, may be D+2.

According to an embodiment, the image decoding apparatus 100 maydetermine a second coding unit 1312 or 1322 and a third coding unit 1314or 1324 of deeper depths by splitting a non-square first coding unit1310 or 1320 based on block shape information indicating a non-squareshape (for example, the block shape information may be expressed as ‘1:NS_VER’ indicating a non-square shape, a height of which is longer thana width, or as ‘2: NS_HOR’ indicating a non-square shape, a width ofwhich is longer than a height).

The image decoding apparatus 100 may determine a second coding unit1302, 1312, or 1322 by splitting at least one of a width and height ofthe first coding unit 1310 having a size of N×2N. That is, the imagedecoding apparatus 100 may determine the second coding unit 1302 havinga size of N×N or the second coding unit 1322 having a size of N×N/2 bysplitting the first coding unit 1310 in a horizontal direction, or maydetermine the second coding unit 1312 having a size of N/2×N bysplitting the first coding unit 1310 in horizontal and verticaldirections.

According to an embodiment, the image decoding apparatus 100 maydetermine the second coding unit 1302, 1312, or 1322 by splitting atleast one of a width and height of the first coding unit 1320 having asize of 2N×N. That is, the image decoding apparatus 100 may determinethe second coding unit 1302 having a size of N×N or the second codingunit 1312 having a size of N/2×N by splitting the first coding unit 1320in a vertical direction, or may determine the second coding unit 1322having a size of N×N/2 by splitting the first coding unit 1320 inhorizontal and vertical directions.

According to an embodiment, the image decoding apparatus 100 maydetermine a third coding unit 1304, 1314, or 1324 by splitting at leastone of a width and height of the second coding unit 1302 having a sizeof N×N. That is, the image decoding apparatus 100 may determine thethird coding unit 1304 having a size of N/2×N/2, the third coding unit1314 having a size of N/4×N/2, or the third coding unit 1324 having asize of N/2×N/4 by splitting the second coding unit 1302 in vertical andhorizontal directions.

According to an embodiment, the image decoding apparatus 100 maydetermine the third coding unit 1304, 1314, or 1324 by splitting atleast one of a width and height of the second coding unit 1312 having asize of N/2×N. That is, the image decoding apparatus 100 may determinethe third coding unit 1304 having a size of N/2×N/2 or the third codingunit 1324 having a size of N/2×N/4 by splitting the second coding unit1312 in a horizontal direction, or may determine the third coding unit1314 having a size of N/4×N/2 by splitting the second coding unit 1312in vertical and horizontal directions.

According to an embodiment, the image decoding apparatus 100 maydetermine the third coding unit 1304, 1314, or 1324 by splitting atleast one of a width and height of the second coding unit 1322 having asize of N×N/2. That is, the image decoding apparatus 100 may determinethe third coding unit 1304 having a size of N/2×N/2 or the third codingunit 1314 having a size of N/4×N/2 by splitting the second coding unit1322 in a vertical direction, or may determine the third coding unit1324 having a size of N/2×N/4 by splitting the second coding unit 1322in vertical and horizontal directions.

According to an embodiment, the image decoding apparatus 100 may splitthe square coding unit 1300, 1302, or 1304 in a horizontal or verticaldirection. For example, the image decoding apparatus 100 may determinethe first coding unit 1310 having a size of N×2N by splitting the firstcoding unit 1300 having a size of 2N×2N in a vertical direction, or maydetermine the first coding unit 1320 having a size of 2N×N by splittingthe first coding unit 1300 in a horizontal direction. According to anembodiment, when a depth is determined based on the length of thelongest side of a coding unit, a depth of a coding unit determined bysplitting the first coding unit 1300 having a size of 2N×2N in ahorizontal or vertical direction may be the same as the depth of thefirst coding unit 1300.

According to an embodiment, a width and height of the third coding unit1314 or 1324 may be ¼ times those of the first coding unit 1310 or 1320.When a depth of the first coding unit 1310 or 1320 is D, a depth of thesecond coding unit 1312 or 1322, the width and height of which are ½times those of the first coding unit 1310 or 1320, may be D+1, and adepth of the third coding unit 1314 or 1324, the width and height ofwhich are ¼ times those of the first coding unit 1310 or 1320, may beD+2.

FIG. 14 illustrates depths that are determinable based on shapes andsizes of coding units, and part indexes (PIDs) that are fordistinguishing the coding units, according to an embodiment.

According to an embodiment, the image decoding apparatus 100 maydetermine various-shape second coding units by splitting a square firstcoding unit 1400. Referring to FIG. 14, the image decoding apparatus 100may determine second coding units 1402 a and 1402 b, 1404 a and 1404 b,and 1406 a, 1406 b, 1406 c, and 1406 d by splitting the first codingunit 1400 in at least one of vertical and horizontal directions based onsplit shape mode information. That is, the image decoding apparatus 100may determine the second coding units 1402 a and 1402 b, 1404 a and 1404b, and 1406 a, 1406 b, 1406 c, and 1406 d, based on the split shape modeinformation of the first coding unit 1400.

According to an embodiment, depths of the second coding units 1402 a and1402 b, 1404 a and 1404 b, and 1406 a, 1406 b, 1406 c, and 1406 d thatare determined based on the split shape mode information of the squarefirst coding unit 1400, may be determined based on the length of a longside thereof. For example, because the length of a side of the squarefirst coding unit 1400 equals the length of a long side of thenon-square second coding units 1402 a and 1402 b, and 1404 a and 1404 b,the first coding unit 2100 and the non-square second coding units 1402 aand 1402 b, and 1404 a and 1404 b may have the same depth, e.g., D.However, when the image decoding apparatus 100 splits the first codingunit 1400 into the four square second coding units 1406 a, 1406 b, 1406c, and 1406 d based on the split shape mode information, because thelength of a side of the square second coding units 1406 a, 1406 b, 1406c, and 1406 d is ½ times the length of a side of the first coding unit1400, a depth of the second coding units 1406 a, 1406 b, 1406 c, and1406 d may be D+1 which is deeper than the depth D of the first codingunit 1400 by 1.

According to an embodiment, the image decoding apparatus 100 maydetermine a plurality of second coding units 1412 a and 1412 b, and 1414a, 1414 b, and 1414 c by splitting a first coding unit 1410, a height ofwhich is longer than a width, in a horizontal direction based on thesplit shape mode information. According to an embodiment, the imagedecoding apparatus 100 may determine a plurality of second coding units1422 a and 1422 b, and 1424 a, 1424 b, and 1424 c by splitting a firstcoding unit 1420, a width of which is longer than a height, in avertical direction based on the split shape mode information.

According to an embodiment, a depth of the second coding units 1412 aand 1412 b, and 1414 a, 1414 b, and 1414 c, or 1422 a and 1422 b, and1424 a, 1424 b, and 1424 c, which are determined based on the splitshape mode information of the non-square first coding unit 1410 or 1420,may be determined based on the length of a long side thereof. Forexample, because the length of a side of the square second coding units1412 a and 1412 b is ½ times the length of a long side of the firstcoding unit 1410 having a non-square shape, a height of which is longerthan a width, a depth of the square second coding units 1412 a and 1412b is D+1 which is deeper than the depth D of the non-square first codingunit 1410 by 1.

Furthermore, the image decoding apparatus 100 may split the non-squarefirst coding unit 1410 into an odd number of second coding units 1414 a,1414 b, and 1414 c based on the split shape mode information. The oddnumber of second coding units 1414 a, 1414 b, and 1414 c may include thenon-square second coding units 1414 a and 1414 c and the square secondcoding unit 1414 b. In this case, because the length of a long side ofthe non-square second coding units 1414 a and 1414 c and the length of aside of the square second coding unit 1414 b are ½ times the length of along side of the first coding unit 1410, a depth of the second codingunits 1414 a, 1414 b, and 1414 c may be D+1 which is deeper than thedepth D of the non-square first coding unit 1410 by 1. The imagedecoding apparatus 100 may determine depths of coding units split fromthe first coding unit 1420 having a non-square shape, a width of whichis longer than a height, by using the above-described method ofdetermining depths of coding units split from the first coding unit1410.

According to an embodiment, the image decoding apparatus 100 maydetermine PIDs for identifying split coding units, based on a size ratiobetween the coding units when an odd number of split coding units do nothave equal sizes. Referring to FIG. 14, a coding unit 1414 b of a centerlocation from among an odd number of split coding units 1414 a, 1414 b,and 1414 c may have a width equal to that of the other coding units 1414a and 1414 c and a height which is two times that of the other codingunits 1414 a and 1414 c. That is, in this case, the coding unit 1414 bat the center location may include two of the other coding unit 1414 aor 1414 c. Therefore, when a PID of the coding unit 1414 b at the centerlocation is 1 based on a scan order, a PID of the coding unit 1414 clocated next to the coding unit 1414 b may be increased by 2 and thusmay be 3. That is, discontinuity in PID values may be present. Accordingto an embodiment, the image decoding apparatus 100 may determine whetheran odd number of split coding units do not have equal sizes, based onwhether discontinuity is present in PIDs for identifying the splitcoding units.

According to an embodiment, the image decoding apparatus 100 maydetermine whether to use a specific splitting method, based on PIDvalues for identifying a plurality of coding units determined bysplitting a current coding unit. Referring to FIG. 14, the imagedecoding apparatus 100 may determine an even number of coding units 1412a and 1412 b or an odd number of coding units 1414 a, 1414 b, and 1414 cby splitting the first coding unit 1410 having a rectangular shape, aheight of which is longer than a width. The image decoding apparatus 100may use PIDs indicating respective coding units so as to identify therespective coding units. According to an embodiment, the PID may beobtained from a sample of a predefined location of each coding unit(e.g., an upper left sample).

According to an embodiment, the image decoding apparatus 100 maydetermine a coding unit at a predefined location from among the splitcoding units, by using the PIDs for distinguishing between the codingunits. According to an embodiment, when the split shape mode informationof the first coding unit 1410 having a rectangular shape, a height ofwhich is longer than a width, indicates to split a coding unit intothree coding units, the image decoding apparatus 100 may split the firstcoding unit 1410 into three coding units 1414 a, 1414 b, and 1414 c. Theimage decoding apparatus 100 may assign a PID to each of the threecoding units 1414 a, 1414 b, and 1414 c. The image decoding apparatus100 may compare PIDs of an odd number of split coding units so as todetermine a coding unit at a center location from among the codingunits. The image decoding apparatus 100 may determine the coding unit1414 b having a PID corresponding to a middle value from among the PIDsof the coding units, as the coding unit at the center location fromamong the coding units determined by splitting the first coding unit1410. According to an embodiment, the image decoding apparatus 100 maydetermine PIDs for distinguishing between split coding units, based on asize ratio between the coding units when the split coding units do nothave equal sizes. Referring to FIG. 14, the coding unit 1414 b generatedby splitting the first coding unit 1410 may have a width equal to thatof the other coding units 1414 a and 1414 c and a height which is twotimes that of the other coding units 1414 a and 1414 c. In this case,when the PID of the coding unit 1414 b at the center location is 1, thePID of the coding unit 1414 c located next to the coding unit 1414 b maybe increased by 2 and thus may be 3. When the PID is not uniformlyincreased as described above, the image decoding apparatus 100 maydetermine that a coding unit is split into a plurality of coding unitsincluding a coding unit having a size different from that of the othercoding units. According to an embodiment, when the split shape modeinformation indicates to split a coding unit into an odd number ofcoding units, the image decoding apparatus 100 may split a currentcoding unit in such a manner that a coding unit of a predefined locationfrom among an odd number of coding units (e.g., a coding unit of acentre location) has a size different from that of the other codingunits. In this case, the image decoding apparatus 100 may determine thecoding unit of the centre location, which has a different size, by usingPIDs of the coding units. However, the PIDs and the size or location ofthe coding unit of the predefined location are not limited to theabove-described examples, and various PIDs and various locations andsizes of coding units may be used.

According to an embodiment, the image decoding apparatus 100 may use apredefined data unit where a coding unit starts to be recursively split.

FIG. 15 illustrates that a plurality of coding units are determinedbased on a plurality of predefined data units included in a picture,according to an embodiment.

According to an embodiment, a predefined data unit may be defined as adata unit where a coding unit starts to be recursively split by usingsplit shape mode information. That is, the predefined data unit maycorrespond to a coding unit of an uppermost depth, which is used todetermine a plurality of coding units split from a current picture. Inthe following descriptions, for convenience of explanation, thepredefined data unit is referred to as a reference data unit.

According to an embodiment, the reference data unit may have apredefined size and shape. According to an embodiment, the referencedata unit may include M×N samples. Herein, M and N may be equal to eachother, and may be integers expressed as powers of 2. That is, thereference data unit may have a square or non-square shape, and may besplit into an integer number of coding units at a later time.

According to an embodiment, the image decoding apparatus 100 may splitthe current picture into a plurality of reference data units. Accordingto an embodiment, the image decoding apparatus 100 may split theplurality of reference data units, which are split from the currentpicture, by using the split shape mode information of each referencedata unit. The operation of splitting the reference data unit maycorrespond to a splitting operation using a quadtree structure.

According to an embodiment, the image decoding apparatus 100 maypreviously determine the minimum size allowed for the reference dataunits included in the current picture. Accordingly, the image decodingapparatus 100 may determine various reference data units having sizesequal to or greater than the minimum size, and may determine one or morecoding units by using the split shape mode information with reference tothe determined reference data unit.

Referring to FIG. 15, the image decoding apparatus 100 may use a squarereference coding unit 1500 or a non-square reference coding unit 1502.According to an embodiment, the shape and size of reference coding unitsmay be determined based on various data units capable of including oneor more reference coding units (e.g., sequences, pictures, slices, slicesegments, tiles, tile groups, largest coding units, or the like).

According to an embodiment, the receiver 110 of the image decodingapparatus 100 may obtain, from a bitstream, at least one of referencecoding unit shape information and reference coding unit size informationwith respect to each of the various data units. An operation ofsplitting the square reference coding unit 1500 into one or more codingunits has been described above with reference to the operation ofsplitting the current coding unit 300 of FIG. 3, and an operation ofsplitting the non-square reference coding unit 1502 into one or morecoding units has been described above with reference to the operation ofsplitting the current coding unit 400 or 450 of FIG. 4. Thus, detaileddescriptions thereof will not be provided herein.

According to an embodiment, the image decoding apparatus 100 may use aPID for identifying the size and shape of reference coding units, todetermine the size and shape of reference coding units according to somedata units previously determined based on a predefined condition. Thatis, the receiver 110 may obtain, from the bitstream, only the PID foridentifying the size and shape of reference coding units with respect toeach slice, each slice segment, each tile, each tile group, or largestcoding unit which is a data unit satisfying a predefined condition(e.g., a data unit having a size equal to or smaller than a slice) amongthe various data units (e.g., sequences, pictures, slices, slicesegments, tiles, tile groups, largest coding units, or the like). Theimage decoding apparatus 100 may determine the size and shape ofreference data units with respect to each data unit, which satisfies thepredefined condition, by using the PID. When the reference coding unitshape information and the reference coding unit size information areobtained and used from the bitstream according to each data unit havinga relatively small size, efficiency of using the bitstream may not behigh, and therefore, only the PID may be obtained and used instead ofdirectly obtaining the reference coding unit shape information and thereference coding unit size information. In this case, at least one ofthe size and shape of reference coding units corresponding to the PIDfor identifying the size and shape of reference coding units may bepreviously determined. That is, the image decoding apparatus 100 maydetermine at least one of the size and shape of reference coding unitsincluded in a data unit serving as a unit for obtaining the PID, byselecting the previously determined at least one of the size and shapeof reference coding units based on the PID.

According to an embodiment, the image decoding apparatus 100 may use oneor more reference coding units included in a largest coding unit. Thatis, a largest coding unit split from a picture may include one or morereference coding units, and coding units may be determined byrecursively splitting each reference coding unit. According to anembodiment, at least one of a width and height of the largest codingunit may be integer times at least one of the width and height of thereference coding units. According to an embodiment, the size ofreference coding units may be obtained by splitting the largest codingunit n times based on a quadtree structure. That is, the image decodingapparatus 100 may determine the reference coding units by splitting thelargest coding unit n times based on a quadtree structure, and may splitthe reference coding unit based on at least one of the block shapeinformation and the split shape mode information according to variousembodiments.

FIG. 16 illustrates a processing block serving as a criterion fordetermining a determination order of reference coding units included ina picture, according to an embodiment.

According to an embodiment, the image decoding apparatus 100 maydetermine one or more processing blocks split from a picture. Theprocessing block is a data unit including one or more reference codingunits split from a picture, and the one or more reference coding unitsincluded in the processing block may be determined according to aspecific order. That is, a determination order of one or more referencecoding units determined in each processing block may correspond to oneof various types of orders for determining reference coding units, andmay vary depending on the processing block. The determination order ofreference coding units, which is determined with respect to eachprocessing block, may be one of various orders, e.g., raster scan order,Z-scan, N-scan, up-right diagonal scan, horizontal scan, and verticalscan, but is not limited to the above-mentioned scan orders.

According to an embodiment, the image decoding apparatus 100 may obtainprocessing block size information and may determine the size of one ormore processing blocks included in the picture. The image decodingapparatus 100 may obtain the processing block size information from abitstream and may determine the size of one or more processing blocksincluded in the picture. The size of processing blocks may be apredefined size of data units, which is indicated by the processingblock size information.

According to an embodiment, the receiver 110 of the image decodingapparatus 100 may obtain the processing block size information from thebitstream according to each specific data unit. For example, theprocessing block size information may be obtained from the bitstream ina data unit such as an image, sequence, picture, slice, slice segment,tile, tile group, or the like. That is, the receiver 110 may obtain theprocessing block size information from the bitstream according to eachof the various data units, and the image decoding apparatus 100 maydetermine the size of one or more processing blocks, which are splitfrom the picture, by using the obtained processing block sizeinformation. The size of the processing blocks may be integer times thatof the reference coding units.

According to an embodiment, the image decoding apparatus 100 maydetermine the size of processing blocks 1602 and 1612 included in thepicture 1600. For example, the image decoding apparatus 100 maydetermine the size of processing blocks based on the processing blocksize information obtained from the bitstream. Referring to FIG. 16,according to an embodiment, the image decoding apparatus 100 maydetermine a width of the processing blocks 1602 and 1612 to be fourtimes the width of the reference coding units, and may determine aheight of the processing blocks 1602 and 1612 to be four times theheight of the reference coding units. The image decoding apparatus 100may determine a determination order of one or more reference codingunits in one or more processing blocks.

According to an embodiment, the image decoding apparatus 100 maydetermine the processing blocks 1602 and 1612, which are included in thepicture 1600, based on the size of processing blocks, and may determinea determination order of one or more reference coding units in theprocessing blocks 1602 and 1612. According to an embodiment,determination of reference coding units may include determination of thesize of the reference coding units.

According to an embodiment, the image decoding apparatus 100 may obtain,from the bitstream, determination order information of one or morereference coding units included in one or more processing blocks, andmay determine a determination order with respect to one or morereference coding units based on the obtained determination orderinformation. The determination order information may be defined as anorder or direction for determining the reference coding units in theprocessing block. That is, the determination order of reference codingunits may be independently determined with respect to each processingblock.

According to an embodiment, the image decoding apparatus 100 may obtain,from the bitstream, the determination order information of referencecoding units according to each specific data unit. For example, thereceiver 110 may obtain the determination order information of referencecoding units from the bitstream according to each data unit such as animage, sequence, picture, slice, slice segment, tile, tile group, orprocessing block. Because the determination order information ofreference coding units indicates an order for determining referencecoding units in a processing block, the determination order informationmay be obtained with respect to each specific data unit including aninteger number of processing blocks.

According to an embodiment, the image decoding apparatus 100 maydetermine one or more reference coding units based on a determinationorder determined according to an embodiment.

According to an embodiment, the receiver 110 may obtain thedetermination order information of reference coding units from thebitstream as information related to the processing blocks 1602 and 1612,and the image decoding apparatus 100 may determine a determination orderof one or more reference coding units included in the processing blocks1602 and 1612 and determine one or more reference coding units, whichare included in the picture 1600, based on the determination order.Referring to FIG. 16, the image decoding apparatus 100 may determinedetermination orders 1604 and 1614 of one or more reference coding unitsin the processing blocks 1602 and 1612, respectively. For example, whenthe determination order information of reference coding units isobtained with respect to each processing block, different types of thedetermination order information of reference coding units may beobtained for the processing blocks 1602 and 1612. When the determinationorder 1604 of reference coding units in the processing block 1602 is araster scan order, reference coding units included in the processingblock 1602 may be determined according to a raster scan order. On thecontrary, when the determination order 1614 of reference coding units inthe other processing block 1612 is a backward raster scan order,reference coding units included in the processing block 1612 may bedetermined according to the backward raster scan order.

According to an embodiment, the image decoding apparatus 100 may decodethe determined one or more reference coding units. The image decodingapparatus 100 may decode an image, based on the reference coding unitsdetermined as described above. A method of decoding the reference codingunits may include various image decoding methods.

According to an embodiment, the image decoding apparatus 100 may obtain,from the bitstream, block shape information indicating the shape of acurrent coding unit or split shape mode information indicating asplitting method of the current coding unit, and may use the obtainedinformation. The split shape mode information may be included in thebitstream related to various data units. For example, the image decodingapparatus 100 may use the split shape mode information included in asequence parameter set, a picture parameter set, a video parameter set,a slice header, a slice segment header, a tile header, or a tile groupheader. Furthermore, the image decoding apparatus 100 may obtain, fromthe bitstream, a syntax element corresponding to the block shapeinformation or the split shape mode information according to eachlargest coding unit, each reference coding unit, or each processingblock, and may use the obtained syntax element.

Hereinafter, a method of determining a split rule according to anembodiment of the disclosure will be described in detail.

The image decoding apparatus 100 may determine a split rule of an image.The split rule may be pre-determined between the image decodingapparatus 100 and the image encoding apparatus 2200. The image decodingapparatus 100 may determine the split rule of the image, based oninformation obtained from a bitstream. The image decoding apparatus 100may determine the split rule based on the information obtained from atleast one of a sequence parameter set, a picture parameter set, a videoparameter set, a slice header, a slice segment header, a tile header,and a tile group header. The image decoding apparatus 100 may determinethe split rule differently according to frames, slices, tiles, temporallayers, largest coding units, or coding units.

The image decoding apparatus 100 may determine the split rule based on ablock shape of a coding unit. The block shape may include a size, shape,a ratio of width and height, and a direction of the coding unit. Theimage encoding apparatus 2200 and the image decoding apparatus 100 maypre-determine to determine the split rule based on the block shape ofthe coding unit. However, an embodiment is not limited thereto. Theimage decoding apparatus 100 may determine the split rule based on theinformation obtained from the bitstream received from the image encodingapparatus 2200.

The shape of the coding unit may include a square and a non-square. Whenthe lengths of the width and height of the coding unit are the same, theimage decoding apparatus 100 may determine the shape of the coding unitto be a square. Also, when the lengths of the width and height of thecoding unit are not the same, the image decoding apparatus 100 maydetermine the shape of the coding unit to be a non-square.

The size of the coding unit may include various sizes, such as 4×4, 8×4,4×8, 8×8, 16×4, 16×8, and to 256×256. The size of the coding unit may beclassified based on the length of a long side of the coding unit, thelength of a short side, or the area. The image decoding apparatus 100may apply the same split rule to coding units classified as the samegroup. For example, the image decoding apparatus 100 may classify codingunits having the same lengths of the long sides as having the same size.Also, the image decoding apparatus 100 may apply the same split rule tocoding units having the same lengths of long sides.

The ratio of the width and height of the coding unit may include 1:2,2:1, 1:4, 4:1, 1:8, 8:1, 1:16, 16:1, 32:1, 1:32 or the like. Also, adirection of the coding unit may include a horizontal direction and avertical direction. The horizontal direction may indicate a case inwhich the length of the width of the coding unit is longer than thelength of the height thereof. The vertical direction may indicate a casein which the length of the width of the coding unit is shorter than thelength of the height thereof.

The image decoding apparatus 100 may adaptively determine the split rulebased on the size of the coding unit. The image decoding apparatus 100may differently determine an allowable split shape mode based on thesize of the coding unit. For example, the image decoding apparatus 100may determine whether splitting is allowed based on the size of thecoding unit. The image decoding apparatus 100 may determine a splitdirection according to the size of the coding unit. The image decodingapparatus 100 may determine an allowable split type according to thesize of the coding unit.

The split rule determined based on the size of the coding unit may be asplit rule pre-determined between the image encoding apparatus 2200 andthe image decoding apparatus 100. Also, the image decoding apparatus 100may determine the split rule based on the information obtained from thebitstream.

The image decoding apparatus 100 may adaptively determine the split rulebased on a location of the coding unit. The image decoding apparatus 100may adaptively determine the split rule based on the location of thecoding unit in the image.

Also, the image decoding apparatus 100 may determine the split rule suchthat coding units generated via different splitting paths do not havethe same block shape. However, an embodiment is not limited thereto, andthe coding units generated via different splitting paths have the sameblock shape. The coding units generated via the different splittingpaths may have different decoding processing orders. Because thedecoding processing orders have been described above with reference toFIG. 12, details thereof are not provided again.

Hereinafter, a method and apparatus for signaling motion vectorresolution information with a high-level syntax which is a group ofinformation that is applied to a predefined data unit group to encode ordecode video in applying Adaptive Motion Vector Resolution (AMVR)according to an embodiment disclosed in the present specification willbe described with reference to FIGS. 17 to 20.

FIG. 17 is a block diagram of a video encoding apparatus according to anembodiment.

In video encoding, inter predication means a prediction method usingsimilarity between a current image and another image. A reference blockthat is similar to a current block of the current image may be detectedfrom a reference image processed before the current image, and adifference in coordinates between the current block and the referenceblock may be represented as a motion vector. Also, differences betweenpixel values of the current block and pixel values of the referenceblock may be represented as residual data. Accordingly, through interprediction for the current block, by outputting an index indicating areference image, a motion vector, and residual data, instead of directlyoutputting image information of the current block, encoding and decodingefficiency may be improved.

A video encoding apparatus 1700 according to an embodiment may include amemory 1710 and at least one processor 1720 connected to the memory1710. Operations of the video encoding apparatus 1700 according to anembodiment may operate as individual processors or by a control of acentral processor. Also, the memory 1710 of the video encoding apparatus1700 may store data received from outside and data (for example, motionvector resolution information, etc.) generated by the processor 1720.

The processor 1720 of the video encoding apparatus 1700 may performmotion prediction on a current block to determine a motion vector and amotion vector resolution of the current block, determine a motion vectorof a candidate block of at least one candidate block as a predictionmotion vector of the current block based on the motion vector resolutionof the current block, determine a residual motion vector of the currentblock using the prediction motion vector of the current block, encodemotion vector resolution information about the motion vector resolutionof the current block with a high-level syntax which is a group ofinformation that is applied to a predefined data unit group includingthe current block, and encode the residual motion vector of the currentblock.

Hereinafter, detailed operations about a video encoding method ofgenerating motion vector resolution information with a high-level syntaxwhen applying an adaptive motion vector resolution in the video encodingapparatus 1700 according to an embodiment will be described withreference to FIG. 18.

FIG. 18 is a flowchart of a video encoding method according to anembodiment.

Referring to FIG. 18, in operation S1810, the video encoding apparatus1700 may perform motion prediction on a current block to determine amotion vector and a motion vector resolution of the current block.

More specifically, the motion vector resolution of the current block maybe determined to have optimal cost by calculating rate-distortion costbased on motion prediction.

In operation S1830, the video encoding apparatus 1700 may determine amotion vector of a candidate block of at least one candidate block as aprediction motion vector of the current block based on the motion vectorresolution of the current block.

The motion vector resolution (hereinafter, also referred to as MVR) mayinclude at least one of a MVR of a ⅛ pel unit, a MVR of a ¼ pel unit, aMVR of a ½ pel unit, a MVR of a 1 pel unit, a MVR of a 2 pel unit, a MVRof a 4 pel unit, and a MVR of a 8 pel unit. However, the MVR is notlimited to the above-mentioned MVRs, and there may be MVRs of pel unitshaving various values.

In the present specification, that a first MVR is greater than a secondMVR means that a pel unit of the first MVR is larger than a pel unit ofthe second MVR. For example, the MVR of the 1 pel unit may be greaterthan the MVR of the ½ pel unit, and the MVR of the ½ pel unit may begreater than the MVR of the ¼ pel unit. Actually, in a case ofdetermining a motion vector with the MVR of the ¼ pel unit, more preciseprediction is possible than a case of determining a motion vector withthe MVR of the 1 pel unit. However, in the present specification, forconvenience of description, differences in magnitude between the MVRswill be described based on pel unit sizes of the MVRs.

The at least one candidate block may be selected from among blocksincluding a spatial block and a temporal block related to the currentblock. The spatial block related to the current block may include atleast one block being spatially adjacent to the current block. Thetemporal block may include a block positioned at the same location asthe current block in a reference image having a Picture Order Count(POC) that is different from a POC of the current block, and at leastone block being spatially adjacent to the block positioned at the samelocation.

In operation S1850, the video encoding apparatus 1700 may determine aresidual motion vector of the current block by using the predictionmotion vector of the current block.

In operation S1870, the video encoding apparatus 1700 may encode motionvector resolution information about the motion vector resolution of thecurrent block with a high-level syntax which is a group of informationthat is applied to a predefined data unit group including the currentblock, and encode the residual motion vector of the current block.

In the present specification, the “motion vector resolution information”means various information related to the motion vector resolution. Forexample, the motion vector resolution information may indicate a motionvector resolution index determined by the high-level syntax andcorresponding to the motion vector resolution, information about amaximum number of motion vector resolution indices, information about aminimum number of motion vector resolution indices, etc., although notlimited thereto.

In the present specification, the “high-level syntax” means a syntaxexisting in a bit stream hierarchically located on a macro block layer.For example, a high-level syntax may indicate a syntax existing in aSequence Parameter Set (SPS) level, a Picture Parameter Set (PPS) level,a slice header level, or a tile header, although not limited thereto.

According to an embodiment, the processor 1720 may be configured tosignal a syntax element representing motion vector resolutioninformation in a sequence parameter set (SPS). A video sequence mayinclude a series of video frames or pictures, and a sequence parameterset may include syntax elements transmitted in a sequence unit.

According to an embodiment, the processor 1720 may be configured tosignal a syntax element representing motion vector resolutioninformation in a picture parameter set (PPS). The picture parameter set(PPS) may be a set of parameters representing several sheets of syntaxesin a picture level.

According to an embodiment, the processor 1720 may be configured tosignal a syntax element representing motion vector resolutioninformation in a slice header. A picture may be split into severalslices. A slice header may represent a syntax in a slice unit.

According to an embodiment, the processor 1720 may be configured tosignal a syntax element representing motion vector resolutioninformation in a tile header. A picture may be split into several tiles.A tile header may represent a syntax in a tile unit.

According to an embodiment, the motion vector resolution information maybe encoded by variable length coding (VLC) or truncated unary coding.

According to an embodiment, by transmitting motion vector resolutioninformation in a high-level syntax, a bit rate may be saved so thatencoding efficiency and performance may be improved.

FIGS. 19 and 20 are a block diagram of a video decoding apparatusaccording to an embodiment and a flowchart of a video decoding methodaccording to an embodiment, respectively corresponding to the videoencoding apparatus and the video encoding method as described above.

FIG. 19 is a block diagram of a video decoding apparatus according to anembodiment.

A video decoding apparatus 1900 according to an embodiment may include amemory 1910 and at least one processor 1920 connected to the memory1910. Operations of the video decoding apparatus 1900 according to anembodiment may operate as individual processors or by a control of acentral processor. Also, the memory 1910 of the video decoding apparatus1900 may store data received from outside and data (for example, motionvector resolution information, etc.) generated by the processor 1920.

The processor 1920 of the video decoding apparatus 1900 may obtainmotion vector resolution information from a bit stream by using ahigh-level syntax which is a group of information that is applied to apredefined data unit group, determine a motion vector resolution of acurrent block included in the predefined data unit group based on themotion vector resolution information, determine a motion vector of acandidate block of at least one candidate block based on the motionvector resolution of the current block, and determine a motion vector ofthe current block by using the motion vector of the candidate block as aprediction motion vector of the current block.

Hereinafter, detailed operations of a video decoding method of usingmotion vector resolution information in a high-level syntax whenapplying an adaptive motion vector resolution in the video decodingapparatus 1900 according to an embodiment will be described withreference to FIG. 20.

FIG. 20 is a flowchart of a video decoding method according to anembodiment.

Referring to FIG. 20, in operation S2010, the video decoding apparatus1900 may obtain motion vector resolution information from a bit streamby using a high-level syntax which is a group of information that isapplied to a predefined data unit group. More specifically, thehigh-level syntax may be one of a sequence level syntax, a picture levelsyntax, a slice level syntax, and a tile level syntax.

According to an embodiment, the processor 1920 may be configured toobtain a syntax element representing motion vector resolutioninformation signaled in a sequence parameter set SPS.

According to an embodiment, the processor 1720 may be configured toobtain a syntax element representing motion vector resolutioninformation signaled in a picture parameter set (PPS).

According to an embodiment, the processor 1720 may be configured toobtain a syntax element representing motion vector resolutioninformation signaled in a slice header.

According to an embodiment, the processor 1720 may be configured toobtain a syntax element representing motion vector resolutioninformation signaled in a tile header.

According to an embodiment, the motion vector resolution information maybe encoded by VLC or truncated unary coding and signaled.

According to an embodiment, by obtaining motion vector resolutioninformation by using a high-level syntax, a bit rate may be saved sothat encoding efficiency and performance may be improved.

In operation S2030, a motion vector resolution of a current blockincluded in the predefined data unit group may be determined based onthe motion vector resolution information.

More specifically, the motion vector resolution of the current blockincluded in the predefined data unit group may be determined based on atleast one of motion vector resolution information which is a group ofvarious information related to the motion vector resolution, forexample, a motion vector resolution index determined by a high-levelsyntax and corresponding to a motion vector resolution, informationabout a maximum number of motion vector resolution indices, informationabout a minimum number of motion vector resolution indices, etc.

In operation S2050, a motion vector of at least one candidate block maybe determined based on the motion vector resolution of the currentblock. More specifically, the video decoding apparatus 1900 maydetermine a candidate block that is used to determine a predictionmotion vector of the current block.

In operation S2070, a motion vector of the current block may bedetermined by using the motion vector of the candidate block as aprediction motion vector of the current block.

According to an embodiment, a motion vector of a candidate block havinga candidate motion vector resolution corresponding to a MVR of thecurrent block may be used as the prediction motion vector of the currentblock, and a residual motion vector of the current block may be added tothe prediction motion vector of the current block to determine a motionvector of the current block.

According to an embodiment, when the candidate motion vector resolutionof the candidate block is different from the motion vector resolution ofthe current block, the motion vector of the candidate block may beadjusted to determine a prediction motion vector of the current block. Amethod of adjusting the motion vector of the candidate block will bedescribed with reference to FIGS. 26A and 26B, later.

According to an embodiment, the motion vector resolution information maychange according to information about at least one of the current block,a previously decoded block, a current tile, a previously decoded tile, acurrent slice, a previously decoded slice, a current picture, and apreviously decoded picture.

FIG. 21 is a view for describing an interpolation method for determiningmotion vectors according to various motion vector resolutions.

The video encoding apparatus 1700 may determine a motion vector of acurrent block according to at least one candidate MVR to perform interprediction on the current block. A supportable candidate MVR may includea MVR of a 2^(k) pel unit (k is an integer). When k is greater than 0,the motion vector may indicate only integer pixels in an interpolatedreference image, and when k is smaller than 0, the motion vector mayindicate sub pixels and integer pixels.

For example, when a minimum MVR has a ¼ pel unit, the video encodingapparatus 1700 may interpolate a reference image to generate sub pixelsof the ¼ pel unit, and determine a motion vector indicating a pixelcorresponding to a candidate MVR, for example, a MVR of a ¼ pel unit, aMVR of a ½ pel unit, a MVR of a 1 pel unit, or a MVR of a 2 pel unit.

For example, the video encoding apparatus 1700 may perform interpolationon the reference image by using a n-tap Finite Impulse Response (FIR)filter to generate sub pixels a to I of the ½ pel unit. In regard of ½sub pixels located in a vertical direction, interpolation may beperformed using A1, A2, A3, A4, A5, and A6 of an integer pel unit togenerate a sub pixel a, and interpolation may be performed using B1, B2,B3, B4, B5, and B6 of an integer pel unit to generate a sub pixel b. Subpixels c, d, e, and f may also be generated by the same method.

Pixel values of the ½ sub pixels located in the vertical direction maybe calculated as follows. For example,a=(A1−5×A2+20×A3+20×A4−5×A5+A6)/32 andb=(B1−5×B2+20×B3+20×B4−5×B5+B6)/32. Pixel values of the sub pixels c, d,e, and f may also be calculated by the same method.

The video encoding apparatus 1700 may perform interpolation on subpixels located in a horizontal direction, as well as the sub pixelslocated in the vertical direction, by using a 6-tap FIR filter. A subpixel g may be generated by using A1, B1, C1, D1, E1, and F1, and a subpixel h may be generated by using A2, B2, C2, D2, E2, and F2.

Pixel values of the sub pixels located in the horizontal direction mayalso be calculated by the same method applied to calculate the pixelvalues of the sub pixels located in the vertical direction. For example,(A1−5×B1+20×C1+20×D1−5×E1+F1)/32.

A sub pixel m of the ½ pel unit located in a diagonal direction may beinterpolated by using another sub pixel of the ½ pel unit. In otherwords, a pixel value of the sub pixel m may be calculated asm=(a−5×b+20×c+20×d−5×e+f)/32.

After the sub pixels of the ½ pel unit are generated, the video encodingapparatus 1700 may generate sub pixels of the ¼ pel unit by usinginteger pixels and the sub pixels of the ½ pel unit. The video encodingapparatus 1700 may perform interpolation by using two adjacent pixels togenerate sub pixels of the ¼ pel unit. Alternatively, the video encodingapparatus 1700 may generate sub pixels of the ¼ pel unit by applying aninterpolation filter directly on pixel values of the integer pixels,without using the pixel values of the sub pixels of the ½ pel unit.

The interpolation filter has been described as an example of a 6-tapfilter, however, the video encoding apparatus 1700 may interpolate apicture by using a filter having another number of taps. For example,the interpolation filter may be a 4-tap filter, a 7-tap filter, an 8-tapfilter, or a 12-tap filter.

FIG. 22A, FIG. 22B, FIG. 22C, and FIG. 22D illustrate locations ofpixels that may be indicated by motion vectors in correspondence to a ¼pel unit MVR, a ½ pel unit MVR, a 1 pel unit MVR, and a 2 pel unit MVR,when a supportable minimum MVR is a ¼ pel unit MVR.

FIG. 22A, FIG. 22B, FIG. 22C, and FIG. 22D show coordinates (representedas black squares) of pixels that may be indicated by motion vectors of a¼ pel unit MVR, a ½ pel unit MVR, a 1 pel unit MVR, and a 2 pel unit MVRwith respect to coordinates (0, 0).

When a minimum MVR is the ¼ pel unit MVR, coordinates of a pixel thatmay be indicated by a motion vector of the ¼ pel unit MVR may be (a/4,b/4) (a and b are integers), coordinates of a pixel that may beindicated by a motion vector of the ½ pel unit MVR may be (2c/4, 2d/4)(c and d are integers), coordinates of a pixel that may be indicated bya motion vector of the 1 pel unit MVR may be (4e/4, 4f/4) (e and f areintegers), and coordinates of a pixel that may be indicated by a motionvector of the 2 pel unit MVR may be (8g/4, 8h/4) (g and h are integers).That is, when the minimum MVR has a 2^(m) (m is an integer) pel unit,coordinates of a pixel that may be indicated by a 2^(n) (n is aninteger) pel unit MVR may be (2^(n−m)*i/2^(−m), 2^(n−m)*j/2^(−m)) (i andj are integers). Although a motion vector is determined according to aspecific MVR, the motion vector may be represented as coordinates in animage interpolated according to the ¼ pel unit.

According to an embodiment, because the video encoding apparatus 1700determines a motion vector in an image interpolated according to aminimum MVR, the video encoding apparatus 1700 may multiply the motionvector (and a prediction motion vector) by an inverse number (forexample, 2^(−m) when the minimum MVR has a 2^(m) (m is an integer) pelunit) of a pel unit value of the minimum MVR to represent a motionvector of an integer unit, such that the motion vector (and theprediction motion vector) can be represented as an integer. The motionvector of the integer unit multiplied by 2^(−m) may be used in the videoencoding apparatus 1700 and the video decoding apparatus 1900.

When a motion vector of a ½ pel unit MVR starting from coordinates (0,0) indicates coordinates (2/4, 6/4) (a motion vector of the ½ pel unitis a value (1, 3) resulting from multiplying the coordinates by aninteger 2) and a minimum MVR has the ¼ pel unit, the video encodingapparatus 1700 may determine, as a motion vector, a value (2, 6)resulting from multiplying the coordinates (2/4, 6/4) indicated by themotion vector by an integer 4.

When a magnitude of a MVR is smaller than the 1 pel unit, the videoencoding apparatus 1700 according to an embodiment may search for ablock that is similar to a current block in a reference image based on asub pel unit, with respect to a motion vector determined in an integerpel unit, in order to perform motion prediction in the sub pel unit.

For example, when a MVR of a current block is a ¼ pel unit MVR, thevideo encoding apparatus 1700 may determine a motion vector in aninteger pel unit, interpolate a reference image to generate sub pixelsin a ½ pel unit, and then search for a prediction block that is mostsimilar to the current block in a range of (−1 to 1, −1 to 1) withrespect to a motion vector determined in an integer pel unit. Then, thevideo encoding apparatus 1700 may interpolate the reference image togenerate sub pixels of the ¼ pel unit, and then search for a predictionblock that is most similar to the current block in the range of (−1 to1, −1 to 1) with respect to the motion vector determined in the ½ pelunit, thereby determining a final motion vector of the ¼ pel unit MVR.

For example, when a motion vector of an integer pel unit is (−4, −3)with respect to coordinates (0, 0), the motion vector may become (−8,−6) (=(−4*2, −3*2) in the ½ pel unit MVR, and, when the motion vectormoves by (0, −1), the motion vector of the ½ pel unit MVR may be finallydetermined as (−8, −7) (=(−8, −6−1)). Also, in the ¼ pel unit MVR, themotion vector may change to (−16, −14) (=(−8*2, −7*2)), and when themotion vector again moves by (−1, 0), the final motion vector of the ¼pel unit MVR may be determined as (−17, −14) (=(−16−1, −14)).

When a MVR of a current block is greater than a 1 pel unit MVR, thevideo encoding apparatus 1700 according to an embodiment may search fora block that is similar to the current block within a reference imagebased on a pel unit that is greater than the 1 pel unit with respect toa motion vector determined in an integer pel unit, in order to performmotion prediction in the greater pel unit. A pixel located in a pel unit(for example, a 2 pel unit, 3 pel unit, or a 4 pel unit) that is greaterthan the 1 pel unit may be referenced as a super pixel.

Hereinafter, a method of determining a motion vector resolution indexrepresenting a motion vector resolution as described above will bedescribed.

FIG. 23 illustrates an example of determining a motion vector resolutionindex using a high-level syntax.

Referring to FIG. 23, motion vector resolution information may includestart resolution location information. The start resolution locationinformation may be information for determining a location of a motionvector resolution index 0 from a predefined motion vector set includinga plurality of resolutions arranged in descending order or ascendingorder. After the motion vector resolution index 0 is determinedaccording to the start resolution location information, motion vectorresolution indices 1, 2, etc. may be sequentially determined.Accordingly, at least one motion vector resolution index may bedetermined from the predefined motion vector set including the pluralityof resolutions sequentially arranged, based on the start resolutionlocation information, and a motion vector resolution of a current blockmay be determined based on the at least one motion vector resolutionindex. More specifically, FIG. 23 illustrates a predefined motion vectorresolution set 2300 arranged in order of ¼, ½, 1, 2, 4, . . . , andstart resolution location information may be information representing alocation indicated by a thick arrow 2310. A resolution corresponding toa MVR index 0 may be determined as the ¼ pel unit which is a resolutionof the location indicated by the thick arrow 2310, based on the startresolution location information. Sequentially, a resolutioncorresponding to a MVR index 1 may be determined as the ½ pel unit, anda resolution corresponding to a MVR index 2 may be determined as the 1pel unit.

FIG. 24 illustrates another example of determining a motion vectorresolution index in a high-level syntax.

Referring to FIG. 24, motion vector resolution information may includemotion vector resolution set information. The motion vector resolutionset information may be information about a motion vector resolution setto be used among a plurality of predefined motion vector resolutionsets. Accordingly, a motion vector resolution set from among theplurality of motion vector resolution sets may be determined based onthe motion vector resolution set information. A motion vector resolutionof a current block may be determined based on at least one motion vectorresolution index determined based on the determined motion vectorresolution set. A first resolution of resolutions sequentially arrangedin descending order or ascending order in the selected motion vectorresolution set may become a motion vector resolution index 0, and thenext resolution may become a motion vector resolution index 1. Morespecifically, in a left part of FIG. 24, three motion vector resolutionsets 2410, 2420, and 2430 are shown, and motion vector resolution setinformation may represent a motion vector resolution set used among aplurality of motion vector resolution sets. In FIG. 24, a motion vectorresolution set 2420 indicated by a thick arrow 2440 may represent amotion vector resolution set to be used for a current block. As shown ina right part of FIG. 24, the motion vector resolution set 2420 may bedetermined as a motion vector resolution set. After the motion vectorresolution set to be used for the current block is determined based onthe motion vector resolution set information, motion vector resolutionindices may be sequentially determined from the motion vector resolutionset. That is, as shown in FIG. 24, a MVR index 0 may be determined asthe ¼ pel unit, a MVR index 1 may be determined as the 1 pel unit, and aMVR index 2 may be determined as the 4 pel unit. When another motionvector resolution set 2410 is selected, a MVR index 0 may be determinedas the ¼ pel unit, a MVR index 1 may be determined as the ½ pel unit,and a MVR index 2 may be determined as the 1 pel unit.

According to another embodiment, the motion vector resolutioninformation may include both information about a motion vectorresolution set to be used among a plurality of motion vector resolutionsets and start resolution information representing a location of a startresolution in the motion vector resolution set. More specifically, whena start resolution location represents a second location by additionalinformation representing a location in the selected motion vectorresolution set 2420 in FIG. 24, a resolution corresponding to a MVRindex 0 may be a 1 pel unit, a resolution corresponding to a MVR index 1may be the 4 pel unit, and a resolution corresponding to a MVR index 2may be the 8 pel unit.

According to another embodiment, the motion vector resolutioninformation may include at least one motion vector resolution indexcorresponding to at least one motion vector resolution, and a motionvector resolution of a current block may be determined based on the atleast one motion vector resolution index. That is, a motion vectorresolution index corresponding to each motion vector resolution may beobtained without using any motion vector resolution set.

According to an embodiment, a motion vector resolution may be determinedaccording to a distance between a current frame POC and a referenceframe POC, instead of a motion vector resolution index.

According to an embodiment, when it is determined that a current frameis close to a reference frame based on a predefined threshold value andan absolute value of a difference between a current frame POC includinga current block and a reference frame POC, a small MVR may be applied,and when it is determined that the current frame is distant from thereference frame, a great MVR may be applied, thereby determining amotion vector resolution of the current block.

According to an embodiment, information representing whether or not touse an absolute value of a difference between a current frame POS and areference frame POC may be obtained from a bit stream by using ahigh-level syntax which is a group of information that is applied to apredefined data unit group. That is, when the absolute value of thedifference is used, a motion vector resolution of the current block maybe determined based on the absolute value of the difference and thepredefined threshold value. More specifically, when the absolute valueof the difference between the current frame POC and the reference framePOC is greater than a predefined first threshold value (that is, whenthe reference frame is relatively distant from the current frame), agreat motion vector resolution (for example, 2, 4, or 8) may be applied,and, when the absolute value of the difference between the current framePOC and the reference frame POC is smaller than a predefined secondthreshold value (that is, when the reference frame is relatively closeto the current frame), a small motion vector resolution (for example, ⅛,¼, or ½) may be applied.

According to an embodiment, predefined resolution informationcorresponding to the absolute value of the difference between thecurrent frame POC and the reference frame POC may be signaled for eachpicture, slice or tile level. That is, a predefined resolution may beapplied according to the distance between the current frame and thereference frame.

According to an embodiment, the motion vector resolution information mayinclude default setting changing information. When the default settingchanging information is 0, a previous default setting may be maintainedas it is, and, when the default setting changing information is 1,additional information for changing a default setting may be obtained toupdate the default setting.

According to an embodiment, the motion vector resolution information mayinclude information about a maximum number of motion vector resolutionindices. More specifically, a MVR index may be determined based oninformation about a maximum number of MVR indices for each picture,slice, or tile. For example, referring to FIG. 23, when informationabout a maximum number of MVR indices indicates that the maximum numberis 4, a MVR index 3 corresponding to the 4 pel unit may be additionallyobtained. Referring to FIG. 24, a MVR index 3 corresponding to the 8 pelunit of the motion vector resolution set 2420 may be obtained.

According to an embodiment, the information about the number of the MVRindices may be encoded by VLC or truncated unary coding and signaled.

According to another embodiment, when an encoding apparatus and adecoding apparatus have information about a minimum number of MVRindices, information about a difference value between the number of MVRindices of a current picture, slice, or tile and the minimum number ofthe MVR indices, instead of the number of MVR indices, may be signaled.More specifically, a case in which a minimum number of MVR indices of anencoding/decoding apparatus is 4 is assumed. In this case, when thenumber of MVR indices of a current picture, slice, or tile is 4, adifference value 0 (=4−4) may be encoded by VLC or truncated unarycoding, and, when the number of the MVR indices of the current picture,slice, or tile is 5, a difference value 1 (5−4) may be encoded by VLC ortruncated unary coding. Also, when the number of the MVR indices of thecurrent picture, slice, or tile is 6, a difference value 2 (6−4) may beencoded by VLC or truncated unary coding.

FIG. 25 illustrates a structure of temporal layers for a Group ofPictures (GOP).

Referring to FIG. 25, information about a maximum number of MVR indices,information about the number of the MVR indices, information about aminimum number of MVR indices, or difference information may changeaccording to the temporal layers. More specifically, information about amaximum number of MVR indices, information about the number of MVRindices, information about a minimum number of MVR indices, ordifference information for each of pictures 1 and 2 corresponding to atemporal layer 0, a picture 3 corresponding to a temporal layer 1,pictures 4 and 7 corresponding to a temporal layer 2, and pictures 5, 6,8, and 9 corresponding to a temporal layer 3 may be determined asdifferent values according to the temporal layers.

Hereinafter, a prediction motion vector adjusting method that isperformed selectively by the video encoding apparatus 1700 and the videodecoding apparatus 1900 according to an embodiment will be describedwith reference to FIGS. 26A and 26B.

When a MVR of a current block is greater than a minimum MVR ofselectable candidate MVRs, the video encoding apparatus 1700 and thevideo decoding apparatus 1900 may adjust a motion vector of a candidateblock that is used as a prediction motion vector of the current block.

In order to adjust a prediction motion vector represented as coordinatesin an image interpolated according to a minimum MVR with a MVR of acurrent block, the video encoding apparatus 1700 and the video decodingapparatus 1900 may adjust the prediction motion vector such that theprediction motion vector indicates pixels being adjacent to a pixelindicated by itself.

For example, as shown in FIG. 26A, to adjust a prediction motion vectorA indicating a pixel 71 of coordinates (19, 20) with respect tocoordinates (0, 0) with a 1 pel unit MVR which is a MVR of a currentblock, the coordinates (19, 27) of the pixel 71 indicated by theprediction motion vector A may be divided by an integer 4 (that is,downscaling). However, there is a case in which coordinates (19/4, 27/4)corresponding to the result of the division do not indicate an integerpel unit.

The video encoding apparatus 1700 and the video decoding apparatus 1900may adjust the downscaled prediction motion vector such that thedownscaled prediction motion vector indicates an integer pel unit. Forexample, coordinates of integer pixels being adjacent to the coordinates(19/4, 27/4) are (16/4, 28/4), (16/4, 24/4), (20/4, 28/4), and (20/4,24/4). In this case, the video encoding apparatus 1700 and the videodecoding apparatus 1900 may adjust the downscaled prediction motionvector A such that the downscaled prediction motion vector A indicatescoordinates (20/4, 28/4) located at a right, upper end, instead of thecoordinates (19/4, 27/4), and then multiply the adjusted coordinates(20/4, 28/4) by an integer 4 (that is, upscaling), thereby causing afinally adjusted prediction motion vector D to indicate a pixel 74corresponding to coordinates (20, 28).

Referring to FIG. 26A, the prediction motion vector A before beingadjusted may indicate the pixel 71, and the finally adjusted predictionmotion vector D may indicate the pixel 74 in an integer unit located atthe right, upper end from the pixel 71.

When the video encoding apparatus 1700 and the video decoding apparatus1900 according to an embodiment adjust a prediction motion vectoraccording to a MVR of a current block, the video encoding apparatus 1700and the video decoding apparatus 1900 may cause the adjusted predictionmotion vector to indicate a pixel located at a right upper end from apixel indicated by the predication motion vector before being adjusted.The video encoding apparatus 1700 and the video decoding apparatus 1900according to another embodiment may cause an adjusted prediction motionvector to indicate a pixel located at a left, upper end from a pixelindicated by the prediction movement vector before being adjusted, apixel located at a left, lower end from the pixel, or a pixel located ata right, lower end from the pixel.

According to an embodiment, when any one of a x coordinate value and a ycoordinate value indicated by the downscaled prediction motion vectorindicates an integer pixel, the video encoding apparatus 1700 and thevideo decoding apparatus 1900 may increase or decrease only theremaining coordinate value not indicating the integer pixel such thatthe increased or decreased coordinate value indicates an integer pixel.That is, when a x coordinate value indicated by the downscaledprediction motion vector indicates an integer pixel, the video encodingapparatus 1700 and the video decoding apparatus 1900 may cause theadjusted prediction motion vector to indicate an integer pixel locatedat an upper end from a pixel indicated by the prediction motion vectorbefore being adjusted or an integer pixel located at a lower end fromthe pixel. Alternatively, when a y coordinate value indicated by thedownscaled prediction motion vector indicates an integer pixel, thevideo encoding apparatus 1700 and the video decoding apparatus 1900 maycause the adjusted prediction motion vector to indicate an integer pixellocated to the left of a pixel indicated by the prediction motion vectorbefore being adjusted or an integer pixel located to the right of thepixel.

When the video encoding apparatus 1700 and the video decoding apparatus1900 adjust a prediction motion vector, the video encoding apparatus1700 and the video decoding apparatus 1900 may select a locationindicated by the adjusted prediction motion vector according to a MVR ofa current block.

For example, referring to FIG. 26B, the video encoding apparatus 1700and the video decoding apparatus 1900 may adjust a prediction motionvector such that the adjusted prediction motion vector indicates a pixellocated at a left, upper end from a pixel 81 indicated by the predictionmotion vector before being adjusted when a MVR of a current block is a ½pel unit MVR, may adjust the prediction motion vector such that theadjusted prediction motion vector indicates a pixel 82 locate at aright, upper end from the pixel 81 indicated by the prediction motionvector before being adjusted when the MVR of the current block is a 1pel unit MVR, and may adjust the prediction motion vector such that theadjusted prediction motion vector indicates a pixel 84 located at aright, lower end from the pixel 81 indicated by the prediction motionvector before being adjusted when the MVR of the current block is a 2pel unit MVR.

The video encoding apparatus 1700 and the video decoding apparatus 1900may determine a pixel indicated by the adjusted prediction motionvector, based on at least one of the MVR of the current block, aprediction motion vector, information about an adjacent block, encodinginformation, and an arbitrary pattern.

The video encoding apparatus 1700 and the video decoding apparatus 1900may adjust a motion vector of a candidate block in consideration of theMVR of the current block and a minimum MVR, according to Equation 1below.pMV′=((pMV>>k)+offset)<<k  [Equation 1]

In Equation 1, pMV′ represents the adjusted prediction motion vector,and k is a value determined according to a difference between theminimum MVR and the MVR of the current block. When the MVR of thecurrent block is a 2^(m) pel unit (m is an integer), the minimum MVR isa 2^(n) pel unit (n is an integer), and m>n, k may be m−n.

According to an embodiment, k may be an index of a MVR, and whencandidate MVRs include a ¼ pel unit MVR, a ½ pel unit MVR, a 1 pel unitMVR, a 2 pel unit MVR, and a 4 pel unit MVR, a MVR corresponding to eachindex of the MVRs has been shown above in Table 1. When the videodecoding apparatus 1900 receives a MVR index from a bit stream, thevideo decoding apparatus 1900 may adjust a motion vector of a candidateblock according to Equation 1 by using the MVR index as k.

Also, in Equation 1, >> or << represents a bit shift operation ofdecreasing or increasing a magnitude of a prediction motion vector.Also, offset means a value that is added to or subtracted from pMVdownscaled according to the k value when the pMV does not indicate aninteger pixel. Offset may be determined as different values for a xcoordinate value and a y coordinate value of a basic MV.

According to an embodiment, the video encoding apparatus 1700 and thevideo decoding apparatus 1900 may change the downscaled pMV according tothe same criterion such that the downscaled pMV indicates an integerpixel.

According to an embodiment, when a x coordinate value and a y coordinatevalue of the downscaled pMV do not indicate an integer pixel, the videoencoding apparatus 1700 and the video decoding apparatus 1900 mayincrease the x coordinate value and the y coordinate value of thedownscaled pMV such that the x coordinate value and the y coordinatevalue of the downscaled pMV indicate an integer value, or decrease the xcoordinate value and the y coordinate value of the downscaled pMV suchthat the x coordinate value and the y coordinate value of the downscaledpMV indicate an integer value. Alternatively, the video encodingapparatus 1700 and the video decoding apparatus 1900 may round off the xcoordinate value and the y coordinate value of the downscaled pMV suchthat the x coordinate value and the y coordinate value of the downscaledpMV indicate an integer value.

According to an embodiment, when the video encoding apparatus 1700 andthe video decoding apparatus 1900 adjust a motion vector of a candidateblock, the video encoding apparatus 1700 and the video decodingapparatus 1900 may omit downscaling and up-scaling of the motion vector,and adjust the motion vector on a coordinate plane in a reference imageinterpolated according to a minimum MVR such that the motion vectorindicates a pel unit corresponding to a MVR of a current block.

Also, according to an embodiment, when the video encoding apparatus 1700and the video decoding apparatus 1900 adjust the motion vector of thecandidate block in consideration of the MVR of the current block and theminimum MVR, the video encoding apparatus 1700 and the video decodingapparatus 1900 may adjust the motion vector according to Equation 2below, instead of Equation 1.pMV′=((pMV+offset)>>k)<<k  [Equation 2]

In Equation 2, offset is applied to an original pMV and then downscalingis performed according to k, unlike Equation 1 of applying offset to adownscaled pMV.

The video encoding apparatus 1700 may search for the motion vector ofthe current block with the MVR of the current block, and obtain, as aresidual motion vector, a difference between the motion vector of thecurrent block and a selectively adjusted prediction motion vector.

The video encoding apparatus 1700 may determine the residual motionvector according to Equation 3 below and encode the residual motionvector. In Equation 3, MV is the motion vector of the current block,pMV′ is the adjusted prediction motion vector, and MVD represents theresidual motion vector.MVD=MV−pMV′  [Equation 3]

When the MVR of the current block is greater than the minimum MVR, thevideo encoding apparatus 1700 may downscale the residual motion vectoraccording to Equation 4, and generate a bit stream including informationrepresenting the downscaled residual motion vector.MVD′=(MVD>>k)  [Equation 4]

In Equation 4, MVD′ represents the downscaled residual motion vector,and k is a value determined according to the difference between the MVRof the current block and the minimum MVR, the k being equal to the k ofEquation 1.

According to an embodiment, the video encoding apparatus 1700 maydownscale the motion vector of the current block and the predictionmotion vector (or the adjusted prediction motion vector) according tothe k value, and then encode a difference between the two values as aresidual motion vector.

According to an embodiment, the video encoding apparatus 1700 maycalculate the downscaled residual motion vector according to Equation 5below, instead of Equation 3 and Equation 4.MVD′=(MV−pMV′)/(R*S)  [Equation 5]

In Equation 5, MVD′ represents the downscaled residual motion vector, MVis the motion vector of the current block, and pMV′ is the adjustedprediction motion vector. Also, R is a pel unit value of the MVR of thecurrent block, and is ¼ when the pel unit value of the MVR of thecurrent block is a ¼ pel unit MVR. Also, S is an inverse number of thepel unit value of the minimum MVR, and S is 4 when the minimum MVR is a¼ pel unit.

The video decoding apparatus 1900 may restore the motion vector of thecurrent block by using the residual motion vector and at least one ofinformation representing the MVR of the current block obtained from thebit stream and information representing the candidate block.

When the MVR of the current block is greater than the minimum MVR, thevideo decoding apparatus 1900 may adjust the prediction motion vectoraccording to Equation 1 or Equation 2.

When the MVR of the current block is greater than the minimum MVR, thevideo decoding apparatus 1900 may upscale residual motion data accordingto Equation 6 below.MVD″=(MVD′<<k)  [Equation 6]

In Equation 6, MVD′ represents the residual motion vector downscaled inthe encoding apparatus, and MVD″ represents the upscaled residual motionvector. The k is a value determined according to a difference betweenthe minimum MVR and the MVR of the current block, the k being equal tothe k of Equation 1.

The video decoding apparatus 1900 may sum a prediction motion vectorselectively adjusted according to a difference in magnitude between theminimum MVR and the MVR of the current block and a selectively upscaledresidual motion vector to decode the motion vector of the current block.

According to an embodiment, the video decoding apparatus 1900 maydetermine the upscaled residual motion vector according to Equation 7below, instead of Equation 6.MVD″=MVD′*(R*S)  [Equation 7]

In Equation 7, MVD′ represents the downscaled residual motion vector, Rrepresents the pel unit value of the MVR of the current block, forexample, ¼ when the pel unit value of the MVR of the current block is a¼ pel unit MVR. Also, S is an inverse number of the pel unit value ofthe minimum MVR, and is 4 when the minimum MVR is a ¼ pel unit.

According to an embodiment, when the MVR of the current block is smallerthan a 1 pel unit MVR, the video decoding apparatus 1900 may interpolatea reference image according to the minimum MVR, and then search for aprediction block according to the motion vector of the current block.Also, when the MVR of the current block is greater than or equal to the1 pel unit MVR, the video decoding apparatus 1900 may search for aprediction block according to the motion vector of the current blockwithout interpolating the reference image.

According to an embodiment, configuration information for a motionvector candidate list may be obtained from a bit stream by using ahigh-level syntax which is a group of information that is applied to apredefined data unit group.

The configuration information for the motion vector candidate listrepresents whether or not to use at least one of a candidate motionvector list for at least one candidate block of the current block and amotion vector list of predefined blocks respectively corresponding tocandidate MVRs of the current block. The configuration information forthe motion vector candidate list may be signaled by VLC or truncatedunary coding.

More specifically, when the signaled configuration information for themotion vector candidate list is 0, both the candidate motion vector listfor at least one candidate block of the current block and the motionvector list of the predefined blocks respectively corresponding to thecandidate MVRs of the current block may be usable. When the signaledconfiguration information for the motion vector candidate list is 10,only the candidate motion vector list for at least one candidate blockof the current block may be usable, and when the signaled configurationinformation for the motion vector candidate list is 11, only the motionvector list of the predefined blocks respectively corresponding to thecandidate MVRs of the current block may be usable. The candidate motionvector list for the at least one candidate block may be a candidatemotion vector list that is used in a skip processing mode, a directprocessing mode, a merge processing mode, or an Adaptive Motion VectorPrediction (AMVP) processing mode that use candidate blocks beingtemporally or spatially adjacent to the current block.

According to another embodiment, the configuration information for themotion vector candidate list may represent whether to use the candidatemotion vector list for the at least one candidate block of the currentblock.

According to another embodiment, the configuration information for themotion vector candidate list may represent only the motion vector listof the predefined blocks respectively corresponding to the candidateMVRs of the current block.

A method of configuring the motion vector list of the predefined blocksrespectively corresponding to the candidate MVRs of the current blockwill be described with reference to FIGS. 27 and 28, later.

FIG. 27 is a view for describing at least one candidate block 1:1 mappedto each of at least one candidate MVR.

At least one candidate block selected from among spatial blocks andtemporal blocks related to a current block may be mapped to eachcandidate MVR.

For example, the spatial blocks may include a left, upper block a, aright, upper block b, a upper, left block c, a upper, right block d, aleft, upper, outer block e, a right, upper, outer block f, a left,lower, outer block g, a right, lower, outer block h, a left, lower blocki, a right, lower block j, a left block k, a right block I, and a upperblock m, which are blocks being adjacent to the current block 50. Thetemporal blocks may include a block n belonging to a reference imagehaving a different POC from that of the current block 50 and located atthe same position as the current block 50, and a block o being adjacentto the block n.

The at least one candidate block selected from among the spatial blocksand the temporal blocks may be mapped to each candidate MVR, and asshown in FIG. 28, a MVR of a ⅛ pel unit may be mapped to the left blockk, a MVR of a ¼ pel unit may be mapped to the upper block m, a MVR of a½ pel unit may be mapped to the left, upper block a, a MVR of a 1 pelunit may be mapped to the upper, left block c, and a MVR of a 2 pel unitmay be mapped to the left, lower block i. The mapping relationship shownin FIGS. 27 and 28 is an example, and various other mappingrelationships may be set.

FIG. 28 illustrates an example of a mapping relationship between atleast one candidate motion vector resolution and at least one candidateblock.

According to the example shown in FIG. 28, when the video encodingapparatus 1700 determines a MVR of a current block as a ⅛ pel unit, thevideo encoding apparatus 1700 may use a motion vector of a left block asa prediction motion vector of the current block. Also, when the videoencoding apparatus 1700 uses a motion vector of a upper block as aprediction motion vector of the current block, the video encodingapparatus 1700 may determine a MVR of the current block as a ¼ pel unit.

Also, when the video decoding apparatus 1900 determines that a MVR of acurrent block is a ⅛ pel unit, the video decoding apparatus 1900 may usea motion vector of a left block as a prediction motion vector of thecurrent block. Also, when the video decoding apparatus 1900 determinesthat a motion vector of a upper block is used as a prediction motionvector of a current block, the video decoding apparatus 1900 maydetermine a MVR of the current block as a ¼ pel unit.

According to an embodiment, a location of a candidate block that ismapped to each of at least one candidate MVR may be determined in theorder of frequently selected prediction motion vectors when motionvectors of a predefined number of blocks in a picture are determinedwith a MVR of an arbitrary pel unit. For example, when a number ofsupportable candidate MVRs is 5, 5 blocks that are frequently selectedas prediction motion vectors from among blocks including spatial blocksand temporal blocks may be mapped to the respective candidate MVRs.

According to an embodiment, when candidate MVRs are 1:1 mapped tocandidate blocks, the candidate MVRs may be arranged in ascending orderaccording to sizes of pel units, the candidate blocks may be arranged indescending order according to the numbers of times at which thecandidate blocks are selected as prediction motion vectors, and then,the candidate MVRs may be 1:1 mapped to the candidate blocksrespectively corresponding to rankings of the candidate MVRs.

Kinds and numbers of candidate MVRs being selectable for a current blockmay change according to information about at least one of the currentblock, a previously decoded block, a current tile, a previously decodedtile, a current slice, a previously decoded slice, a current picture,and a previously decoded picture.

Also, locations of candidate blocks respectively mapped to the candidateMVRs being selectable for the current block may change according toinformation about at least one of the current block, a previouslydecoded block, a current tile, a previously decoded tile, a currentslice, a previously decoded slice, a current picture, and a previouslydecoded picture.

The kinds and numbers of candidate MVRs being selectable for a currentblock, and locations of candidate blocks respectively mapped to thecandidate MVRs being selectable for the current block may be determinedbased on the same criterion by the video encoding apparatus 1700 and thevideo decoding apparatus 1900, and accordingly, although the videoencoding apparatus 1700 encodes an index representing a MVR of a currentblock or an index representing a candidate block for the current blockand transmits the index to the video decoding apparatus 1900, the videodecoding apparatus 1900 may determine the MVR or the candidate blockcorresponding to the index.

According to an embodiment, the video encoding apparatus 1700 maydetermine whether to execute at least one processing mode of a pluralityof processing modes included in at least one processing among predictionprocessing, transform processing, and filtering processing for encodingthe current block, based on the motion vector resolution of the currentblock. Information about whether to execute the at least one processingmode may be encoded with a high-level syntax.

According to an embodiment, the video decoding apparatus 1900 may obtaininformation about whether to execute at least one processing mode basedon the motion vector resolution of the current block from the pluralityof processing modes included in at least one processing of predictionprocessing, transform processing, and filtering processing for decodingthe current block, from a bit stream, by using the high-level syntax.The video decoding apparatus 1900 may decode the current block based onthe information about whether to execute the at least one processingmode.

According to an embodiment, the information about whether to execute theat least one processing mode may include default setting changinginformation, and when the default setting changing informationrepresents that whether to execute a processing mode changes, theinformation about whether to execute the at least one processing modemay be updated. Also, when the default setting changing informationrepresents that whether to execute a processing mode does not change,the information about whether to execute the at least one processingmode may be maintained. More specifically, when the default settingchanging information is 0, the information about whether to execute theat least one processing mode may be used as it is, and when the defaultsetting changing information is 1, the information about whether toexecute the at least one processing mode may be updated.

Referring to FIG. 25, the information about whether to execute the atleast one processing mode may be classified according to temporallayers. More specifically, information about whether to execute at leastone processing mode for the pictures 1 and 2 corresponding to thetemporal layer 0, the picture 3 corresponding to the temporal layer 1,the pictures 4 and 7 corresponding to the temporal layer 2, and thepictures 5, 6, 8, and 9 corresponding to the temporal layer 3 may bedetermined as different values according to the temporal layers.

Also, when the default setting changing information represents thatwhether to execute a processing mode changes even on the same temporallayer, the information about whether to execute at least one processingmode may be updated. More specifically, information about whether toexecute at least one processing mode for the picture 5 of the temporallayer 3 may be maintained at it is when information 0 indicating thatwhether to execute a processing mode is maintained is transmitted fromthe picture 6, and when information 1 indicating that whether to executea processing mode changes is transmitted from the picture 7, theinformation about whether to execute at least one processing mode may beupdated.

Processing modes including prediction processing, transform processing,and filtering processing for encoding and decoding a current block willbe described with reference to FIG. 29, below.

FIG. 29 illustrates processing modes respectively included in predictionprocessing, transform processing, and filtering processing.

According to an embodiment, the prediction processing may include atleast one of an inter prediction processing mode, an intra predictionprocessing mode, a skip processing mode, a direct processing mode, anAMVP processing mode, an affine processing mode, a Bi-Optical Flow (BIO)processing mode, a Decoder-side Motion Vector Derivation (DMVD)processing mode, an Illumination Compensation (IC) processing mode, anOverlapped Block Motion Compensation (OBMC) processing mode, an InterPrediction Refinement (IPR) processing mode, and a prediction blockgeneration mode.

According to an embodiment, the transform processing may include atleast one of a Multiple Transform (MT) processing mode, a Non-SeparableSecondary Transform (NSST) processing mode, a Rotational Transform (ROT)processing mode, a Discrete Sine Transforms (DST) processing mode, and aDiscrete Cosine Transforms (DCT) processing mode.

According to an embodiment, the filtering processing may include atleast one of a deblocking processing mode, a Sample Adaptive Offset(SAO) processing mode, a Bilateral Filter (BF) processing mode, and anAdaptive Loop Filter (ALF) processing mode.

First, the processing modes included in the prediction processing, thetransform processing, and the filtering processing will be brieflydescribed. For definite descriptions about the embodiments according tothe disclosure, descriptions about detailed algorithms for the followingprocessing modes will be omitted.

The inter prediction processing mode means a processing method usingsimilarity between a current image and another image. A reference blockthat is similar to a current block of the current image may be detectedfrom among reference images decoded earlier than the current image, anda prediction block may be determined from the reference block. Adistance in coordinates between the current block and the predictionblock may be represented as a motion vector, and differences betweenpixel values of the current block and pixel values of the predictionblock may be represented as residual data. Accordingly, through interprediction for the current block, by outputting an index indicating areference image, a motion vector, and residual data, instead of directlyoutputting image information of the current block, encoding and decodingefficiency may be improved.

The intra prediction processing mode means a processing method usingspatial similarity in an image. A prediction block that is similar to acurrent block may be generated from pixel values being adjacent to thecurrent block, and differences between pixel values of the current blockand pixel values of the prediction block may be represented as residualdata. By outputting information about the prediction block generationmode and residual data, instead of directly outputting image informationof the current block, encoding and decoding efficiency may be improved.

The skip processing mode may search for a reference block in a referenceimage by using motion information of an adjacent block as motioninformation of a current block. A prediction block determined from thereference block may be determined as the current block.

The direct processing mode is a method of the inter predictionprocessing mode, and may search for a reference block in a referenceimage by using motion information of an adjacent block as motioninformation of a current block, and determine a prediction block fromthe reference block. Then, the direct processing mode may restore thecurrent block with a combination of residual data and the predictionblock. The direct processing mode may be referenced as the mergeprocessing mode.

The AMVP processing mode is a method of the inter prediction processingmode, and may sum a motion vector of an adjacent block and a residualmotion vector to determine a motion vector of a current block, andsearch for a reference block corresponding to the motion vector in areference image specified based on a reference image list and areference image index. Then, the AMVP processing mode may restore thecurrent block with a combination of a prediction block and residualdata.

The affine processing mode represents processing of transforming orinverse-transforming a motion vector of a block representing atranslation motion into a motion vector representing a rotation motion,zoom-in, or zoom-out.

The BIO processing mode represents sample-wise motion vector improvementprocessing that is performed with respect to block-wise motioncompensation for bi-directional prediction.

The DMVD processing mode is technology of inducing a motion vector in adecoder side, and induces a motion vector of a current block throughtemplate matching or bilateral matching.

The IC processing mode is technology of increasing prediction efficiencyby compensating for illumination of a current block and/or a referenceblock in a reference image to increase prediction efficiency whendecoding the current block in the inter prediction processing mode.

The OBMC processing mode is technology of weighted-summing restoredpixels at a current location by a motion of adjacent blocks and restoredpixels of a current block to perform motion compensation.

The IPR processing mode is technology of changing pixel values of aprediction block determined from a reference image of a current block byusing a linear model between a restored block and a prediction block.

The prediction block generation mode is a method of generating aprediction block of a current block in the inter prediction processingmode, and for example, the prediction block generation mode may includea plurality of different prediction block generation modes. The HighEfficiency Video Coding (HEVC) discloses a total of 35 types of modesincluding a Intra_Planar mode, an Intra_DC mode, and an Intral_Angularmode, as prediction block generation modes.

The MT processing mode is technology of sequentially using a pluralityof transform kernels to transform residual data in a spatial domain intoresidual data in a frequency domain, or inverse-transform residual datain a frequency domain into residual data in a spatial domain.

The NSST processing mode is transform technology that is performedbetween core transform and quantization and between dequantization andinverse core transform, and the NSST processing mode may be applied onlyto some area of a current block.

The ROT processing mode is technology of partially exchanging at leastones of rows and columns of a frequency coefficient matrix. Partiallyexchanging rows or columns may mean partially exchanging values of tworows or columns by using a specific function such as a trigonometricalfunction, not 1:1 exchanging values of specific rows or columns.

The DST processing mode is technology of transforming residual data in aspatial domain into residual data in a frequency domain orinverse-transforming residual data in a frequency domain into residualdata in a spatial domain by using DST transform kernels.

The DCT processing mode is technology of transforming residual data in aspatial domain into residual data in a frequency domain orinverse-transforming residual data in a frequency domain into residualdata in a spatial domain by using DCT transform kernels.

The deblocking processing mode is technology for improving a blockingartifact which is distortion generated at boundaries between blocks.

The SAO processing mode is technology of adding an offset to a restoredsample to minimize an error between a restored image and an originalimage.

The BF processing mode is technology of replacing pixel values of arestored block with weighted averages of pixel values of a current blockand pixel values of an adjacent block.

The ALF processing mode is technology of changing pixel values by usinga filter selected from among a plurality of filters for each of aplurality of pixel groups included in a restored current block.

According to an embodiment, the order of determinations on whether toapply the processing modes shown in FIG. 29 may have been set inadvance. When whether to apply a processing mode is determined accordingto a preset syntax, no determination on whether to apply the otherprocessing modes may be made according the result of the determination.For example, after whether to apply the skip processing mode isdetermined in prediction processing, whether to apply a processing modemay be determined in the order of the inter prediction processing mode,the direct processing mode, and the AMVP processing mode. After whetherto apply the skip processing mode is determined, whether to apply theinter prediction processing mode may be determined. When it isdetermined that the skip processing mode is applied, no determination onwhether to apply the inter prediction processing mode, the directprocessing mode, and the AMVP processing mode may be made. That is,acquisition of information related to the inter prediction processingmode, the direct processing mode, and the AMVP processing mode may beskipped.

According to an embodiment, when a processing mode that is applicable toa current block is specified based on a MVR of the current block, thevideo decoding apparatus 1900 may decode the current block in thespecified processing mode.

According to an embodiment, the video decoding apparatus 1900 maydetermine a processing mode that is applicable to the current block,based on the MVR corresponding to the current block. The applicableprocessing mode may be a processing mode having probability of beingapplied to the current block, and the applicable processing mode may beactually applied to the current block or may be not applied to thecurrent block according to information included in a bit stream. Anon-applicable processing mode which will be described later means aprocessing mode having no probability of being applied to a currentblock.

The MVR of the current block may mean precision of a location of a pixelthat may be indicated by a motion vector of the current block amongpixels included in a reference image (or an interpolated referenceimage). The MVR of the current block may be selected from among at leastone candidate MVR. The at least one candidate MVR may include at leastone of, for example, a MVR of a ⅛ pel unit, a MVR of a ¼ pel unit, a MVRof a ½ pel unit, a MVR of a 1 pel unit, a MVR of a 2 pel unit, a MVR ofa 4 pel unit, and a MVR of a 8 pel unit, although not limited thereto.According to an implementation example, the candidate MVR may includeonly a MVR.

FIGS. 30 to 32 illustrate examples of applicable processing modes ornon-applicable processing modes preset for MVRs.

Referring to FIG. 30, when a MVR of a current block is a ¼ pel unit, itmay be determined that the affine processing mode is applicable to thecurrent block, and when a MVR of a current block is a ½ pel unit, a 1pel unit, or a 2 pel unit, it may be determined that the DMVD processingmode is applicable to the current block.

Referring to FIG. 31, when a MVR of a current block is a ¼ pel unit, itmay be determined that the DST processing mode is non-applicable to thecurrent block, and when a MVR of a current block is a ½ pel unit, a 1pel unit, or a 2 pel unit, it may be determined that the ROT processingmode is non-applicable to the current block

Also, referring to FIG. 32, when a MVR of a current block is a ¼ pelunit, it may be determined that the affine processing mode and the ICprocessing mode are applicable to the current block, and the BFprocessing mode is non-applicable to the current block. When a MVR of acurrent block is a ½ pel unit, a 1 pel unit, or a 2 pel unit, it may bedetermined that the ROT processing mode is applicable to the currentblock, and the OBMC processing mode and the SAO processing mode arenon-applicable to the current block.

According to an embodiment, the video decoding apparatus 1900 maydetermine at least one applicable processing mode for a current blockbased on a motion vector of the current block, and obtain informationabout the applicable processing mode from a bit stream. The informationabout the applicable processing mode may include, for example,information about at least one of whether to apply a processing mode anddetailed setting content related to the processing mode.

The video decoding apparatus 1900 may obtain the information about theapplicable processing mode from the bit stream, and decode the currentblock based on the applicable processing mode. According to anembodiment, the video decoding apparatus 1900 may determine whether toapply the applicable processing mode to the current block based on theinformation obtained from the bit stream, and decode the current blockin the applicable processing mode according to the result of thedetermination.

According to an embodiment, decoding the current block in the applicableprocessing mode does not mean applying only the applicable processingmode to the current block. According to an embodiment, the videodecoding apparatus 1900 may process the current block according toanother processing mode of which application needs to be determinedearlier than the applicable processing mode, in a preset order, in otherwords, according to a preset syntax, and then apply the applicableprocessing mode to the current block. Alternatively, the video decodingapparatus 1900 may process the current block according to the applicableprocessing mode, and then decode the current block according to theother processing mode of which application is determined according tothe preset syntax.

For example, when an applicable processing mode corresponding to a MVRis the affine processing mode, the video decoding apparatus 1900 mayperform prediction processing on the current block according to theaffine processing mode, and apply a processing mode included intransform processing and a processing mode included in filteringprocessing to the prediction-processed current block to decode thecurrent block.

For example, when an applicable processing mode corresponding to a MVRis the SAO processing mode, the video decoding apparatus 1900 may applythe SAO processing mode to a current block to which both a processingmode of prediction processing and a processing mode of transformprocessing are applied, to decode the current block.

So far, various embodiments have been described. It will be apparentthat those of ordinary skill in the technical art to which thedisclosure belongs may readily make various modifications theretowithout changing the essential features of the disclosure. Therefore, itshould be understood that the disclosed embodiments described hereinshould be considered in a descriptive sense only and not for purposes oflimitation. The scope of the disclosure is defined in the accompanyingclaims rather than the above detailed description, and it should benoted that all differences falling within the claims and equivalentsthereof are included in the scope of the disclosure.

Meanwhile, the embodiments of the disclosure may be written as a programthat is executable on a computer, and implemented on a general-purposedigital computer that operates a program using a computer-readablerecording medium. The computer-readable recording medium may include astorage medium, such as a magnetic storage medium (for example, ROM, afloppy disk, a hard disk, etc.) and an optical reading medium (forexample, CD-ROM, DVD, etc.).

The invention claimed is:
 1. A video decoding method comprising:obtaining, from a bitstream, a motion vector difference resolutionindex; obtaining motion vector difference resolution set information;determining a motion vector difference resolution of a current block,based on the motion vector difference resolution index and the motionvector difference resolution set information; obtaining, from thebitstream, motion vector difference of the current block; adjusting themotion vector difference based on the motion vector differenceresolution; and obtaining a motion vector of the current block by usinga prediction motion vector and the adjusted motion vector difference,wherein the motion vector difference resolution set informationindicates one motion vector difference resolution set among a pluralityof motion vector difference resolution sets, the one motion vectordifference resolution set including a plurality of motion vectordifference resolutions, wherein the plurality of motion vectordifference resolutions are predetermined and the motion vectordifference resolution index corresponds to one motion vector differenceresolution among the plurality of motion vector difference resolutionsincluded in the motion vector difference resolution set which isindicated by the motion vector difference resolution set information,wherein the prediction motion vector is obtained by using a motionvector of a neighboring block of the current block.